Varenicline compound and process of manufacture thereof

ABSTRACT

The present disclosure relates to the field of synthesizing substantially pure varenicline and its intermediates. It also relates to the pharmaceutical compositions comprising varenicline and the method of use of these pharmaceutical compositions for smoking cessation.

RELATED APPLICATION

This application claims priority to U.S. Provisional Application SerialNo. 63/319,043 filed on Mar. 11, 2022, which is incorporated herein byreference in its entirety to the full extent permitted by law.

TECHNICAL FIELD

The present disclosure relates to the synthesis of vareniclinesubstantially free of impurities. It also relates to pharmaceuticalcompositions comprising substantially pure varenicline, and to methodsof treating nicotine dependency, addiction and withdrawal byadministering such compound.

BACKGROUND

Varenicline tartrate salt,7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]-benzazepinetartrate has the following formula:

Varenicline base and various salts thereof are described in U.S. PatentNo. 6,410,550, EP1044189, EP1659114, and EP1866308.

Varenicline L-tartrate and its crystalline forms A, B and C aredescribed in the U.S. Pat. Nos. 6,890,927 and 7,265,119, characterizedby XRPD peaks at 6.1, 12.2, 13.0, 14.7, 16.8, 19.4, 21.9, 24.6 (form A);characterized by XRPD peaks at 5.9, 12.8, 14.4, 15.3, 16.9, 17.2, 21.8,23.8, 25.1 (form B); and characterized by XRPD peaks at 5.9, 11.8, 16.5,21.2, 23.1, 23.8, 26.5 (form C).

WO2008060487 describes crystalline forms of varenicline base andintermediates thereof. It also describes the polymorphs for vareniclinefree base (Form A, C, D, and E). EP2260037 describes polymorphs forvarenicline free base (Form I, and II), and CN103896943 describes hemitartrate salt.

Varenicline tartrate was marketed by Pfizer under the trade name ofCHANTIX® as a partial agonist selective for certain subtypes ofnicotinic receptors and indicated for smoking cessation. However, due tounacceptable level of nitrosamine impurities in CHANTIX®, the productwas withdrawn. Accordingly, there is a need for an varenicline activepharmaceutical ingredient (“API”) that has an acceptable level ofnitrosamine impurities.

SUMMARY

The present disclosure provides an improved process of manufacturingsubstantially pure varenicline for use as an active pharmaceuticalingredient. In certain embodiments, the process results in vareniclinetartrate having less than 100 ppm of N-nitroso-varenicline impurity per1 mg of varenicline free base, or per 0.5 mg varenicline free base, orless than 50 ppm, or less than 25 ppm, or less than 10 ppm, or less than5 ppm as measured by the LC-ESI-HRMS Method for the Determination ofVarenicline Nitroso-Drug Substance Related Impurity, U.S. FDA, August 6,2021, https://www.fda.gov/media/151470/download (accessed Feb. 27, 2022)(the “LC-ESI-HRMS Method”); HPLC or LCMS.

The present disclosure further describes a process for preparation of7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3]benzazepine,(2R,3R)-2,3-dihydroxy butanedioate maltodextrin, comprisingthe steps of:

(a) contacting a reducing agent with1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanoneto form 1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone;

(b) contacting Glyoxal solution in water, a catalyst and a solvent with1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanoneto form1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone;

(c) contacting sodium carbonate solution and methanol with145,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanoneto form crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine;

(d) purifying crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine byacid-base treatment substantially eliminate impurities and to formpurified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine; and

(e) contacting purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine withL-(+) tartaric acid, maltodextrin, methanol and water to form7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate. maltodextrin premix(1:10).

In certain aspects, the process results in the7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate. maltodextrin premix(1:10) being substantially free from nitrosamine impurities,particularly N-nitroso-varenicline.

In one embodiment, crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine isisolated from a reaction mass by a process, comprising the steps of:

(a) cooling and filtering the reaction mass to form a filtrate and a wetcake;

(b) distilling the filtrate to remove methanol;

(c) adding sodium chloride solution to the distilled filtrate;

(d) extracting raw 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine using methylene chloride and washing with sodiumchloride solution;

(e) treating raw 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine with activated carbon, washing with methylenedichloride and filtering the methylene dichloride through a hyflo bed;

(f) distilling out methylene dichloride followed by co-distilling withtertiary butyl methyl ether to form a semi dried product;

(g) adding tertiary butyl methyl ether to the semi dried product; and

(i) isolating crude 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine.

In another embodiment, the above process results in about 1 mg of thepurified 7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino [2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate. maltodextrin premix(1:10) having less than 25 ppm N-nitroso-varenicline impurity, or about18.5 ppm or less of N-nitroso-varenicline impurity.

The process of the present disclosure may employ a spray drying stepthat produces nearly spherical shaped particles, and wherein the7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate is essentially uniformlydispersed in maltodextrin matrix in the particles.

The present disclosure also relates to a method of treating nicotinedependency, addiction and withdrawal in a subject in need thereof,comprising providing a pharmaceutical composition comprising about 0.5mg to about 2 mg substantially pure varenicline tartrate; and orallyadministering the composition in one or more daily doses, wherein thesubject receives a total of no more than about 37 ng ofN-nitroso-varenicline impurity per day. In one embodiment, thecomposition comprises about 1.7 mg of varenicline tartrate that has lessthan 25 ppm of N-nitroso-varenicline impurity as measured by theLC-ESI-HRMS Method, HPLC or LCMS. In another embodiment, the compositioncomprises about 0.85 mg of varenicline tartrate that has less than 25ppm of N-nitroso-varenicline impurity as measured by the LC-ESI-HRMSMethod, HPLC or LCMS.

In another aspect, the composition is orally administered one weekbefore a date set by the subject to attempt to stop smoking. Thetreatment regimens described herein are effective in the subject to quitsmoking between days 8 and 35 of treatment.

In some embodiments, the composition is administered at a dose of about1 mg varenicline free base twice daily, or wherein the composition isadministered in a regimen comprising:

(a) 0.5 mg varenicline free base once daily for days 1-3 of thetreatment;

(b) 0.5 mg varenicline free base twice daily for days 4-7 of thetreatment; and

(c) 1 mg varenicline free base twice daily after day 7 of the treatment.

The present disclosure further relates to a pharmaceutical composition,comprising substantially pure varenicline tartrate and at least oneexcipient. The composition may comprise about 0.5 mg to about 2 mgvarenicline tartrate and is in the form of a tablet or capsule. In oneembodiment, the N-nitroso-varenicline impurity is present in an amountof less than 50 ppm per tablet or capsule as measured by the LC-ESI-HRMSMethod, HPLC or LCMS.

The pharmaceutical compositions of the present disclosure may containone or more excipients such as croscarmellose sodium, microcrystallinecellulose, stearic acid, hydroxypropyl cellulose, hypromellose, talc,and titanium dioxide. In some embodiments, the inventive solid dosageforms comprise about 0.5 mg varenicline free base and about 5 ppm orless of N-nitroso-varenicline impurity, or 1 mg varenicline free baseand about 5 ppm or less of N-nitroso-varenicline impurity.

Additional embodiments of the present processes, compositions, methodsof treatment and the like will be apparent from the followingdescription, drawings, examples, and claims. As can be appreciated fromthe foregoing and following description, each and every featuredescribed herein, and each and every combination of two or more of suchfeatures, is included within the scope of the present disclosureprovided that the features included in such a combination are notmutually inconsistent. In addition, any feature or combination offeatures may be specifically excluded from any embodiment or aspect.Additional aspects and embodiments are set forth in the followingdescription and claims, particularly when considered in conjunction withthe accompanying examples and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The foregoing features of embodiments will be more readily understood byreference to the following detailed description, taken with reference tothe accompanying drawings, in which:

FIG. 1 is a summary of the purification of varenicline free base.

FIG. 2 is a SEM image of crystalline API-PAT (crystalline vareniclinetartrate salt).

FIG. 3 is a SEM image of maltodextrin (Glucidex 12D).

FIG. 4 is a SEM image of API Premix (varenicline tartrate: Maltodextrin−1:10)_PAT.

FIG. 5 is a SEM image of API +Maltodextrin (Physical Mix) (1:10).

FIG. 6A is an X-ray diffractogram of varenicline tartrate shows presenceof signature peaks for crystalline form B. FIG. 6B is a list of thepeaks shown in FIG. 6A.

FIG. 7 is an X-ray diffractogram of varenicline tartrate maltodextrinpremix (1:10) exists in an amorphous form. No crystalline peakscharacteristic of crystalline varenicline tartrate is observed in thediffractogram.

FIG. 8A is a specificity chromatogram of HPLC method: RS METHOD-I. FIGS.8B-8D are segments of the chromatograph of FIG. 8A. The specificitystudy chromatogram of the impurities viz. N-methyl Varenicline,Varenicline N-Glucoside in RS METHOD-I are provided in FIG. 8E.

FIG. 9A is a specificity chromatogram of HPLC method: RS METHOD-II. FIG.9B and FIG. 9C are segments of the chromatograph of FIG. 9A.

FIG. 10A is a specificity chromatogram of HPLC method: RS METHOD-III.FIG. 10B and FIG. 10C are segments of the chromatograph of FIG. 9A.

FIG. 11 is a graphical presentation of purification of varenicline freebase to eliminate nitrosamine impurities using organic or inorganicacids and also by catalytic hydrogenation in the presence of palladiumon charcoal.

DETAILED DESCRIPTION

The various aspects and embodiments will now be fully described herein.These aspects and embodiments may, however, be embodied in manydifferent forms and should not be construed as limiting; rather, theseembodiments are provided so the disclosure will be thorough andcomplete, and will fully convey the scope of the present subject matterto those skilled in the art. All publications, patents and patentapplications cited herein, whether supra or infra, are herebyincorporated by reference in their entirety.

A. DEFINITIONS

Unless defined otherwise, all terms and phrases used herein include themeanings that the terms and phrases have attained in the art, unless thecontrary is clearly indicated or clearly apparent from the context inwhich the term or phrase is used. Although any methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, particular methods andmaterials are now described.

Unless otherwise stated, the use of individual numerical values arestated as approximations as though the values were preceded by the word“about” or “approximately.” Similarly, the numerical values in thevarious ranges specified in this application, unless expressly indicatedotherwise, are stated as approximations as though the minimum andmaximum values within the stated ranges were both preceded by the word“about” or “approximately.” In this manner, variations above and belowthe stated ranges can be used to achieve substantially the same resultsas values within the ranges. As used herein, the terms “about” and“approximately” when referring to a numerical value shall have theirplain and ordinary meanings to a person of ordinary skill in the art towhich the disclosed subject matter is most closely related or the artrelevant to the range or element at issue. The amount of broadening fromthe strict numerical boundary depends upon many factors. For example,some of the factors which may be considered include the criticality ofthe element and/or the effect a given amount of variation will have onthe performance of the claimed subject matter, as well as otherconsiderations known to those of skill in the art. As used herein, theuse of differing amounts of significant digits for different numericalvalues is not meant to limit how the use of the words “about” or“approximately” will serve to broaden a particular numerical value orrange. Thus, as a general matter, “about” or “approximately” broaden thenumerical value. Also, the disclosure of ranges is intended as acontinuous range including every value between the minimum and maximumvalues plus the broadening of the range afforded by the use of the term“about” or “approximately.” Consequently, recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, and eachseparate value is incorporated into the specification as if it wereindividually recited herein.

“Diamide impurity” is Bis (7,8,9,1 0-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]-benzazepine)-amide.

“Diamino Nitrosamine” is10-nitroso-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2,4,6-triene-4,5-diamine.

The term “LOD” means limit or level of detection.

The term “LOQ” means limit of quantitation.

“Mononitro Deprotected” is7-nitro-2,3,4,5-tetrahydro-1H-1,5-methano-3-benzazepine.

“N-Formyl Varenicline” is 6,7,9,10-Tetrahydro-6,10-methano-8H-pyrazino[2,3-h][3]benzazepine-8-carboxaldehyde.

The terms “nitrosamine varenicline impurity,” “varenicline nitrosamineimpurity” and “N-nitroso-varenicline” are used interchangeably herein.

The terms “nitrosamine impurities” is used for Dinitro Nitrosoamineimpurity(4,5-Dinitro-10-nitroso-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2,4,6-triene);Diamino Nitrosoamine impurity(10-nitroso-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2,4,6-triene-4,5-diamine);Nitroso Varenicline impurity(7,8,9,10-tetrahydro-8-nitroso-6,10-Methano-6H-pyrazino [2,3-h][3]benzazepine); or a combination thereof.

“N-Methyl Varenicline” is 6,10-methano-6H-pyrazino [2,3-h][3]benzazepine 7,8,9,10-Tetrahydo-8-methyl.

“Optional” or “optionally” means that the subsequently describedelement, component or circumstance may or may not occur, so that thedescription includes instances where the element, component, orcircumstance occurs and instances where it does not.

The term “premix” as used herein refers to maltodextrin and vareniclinetartrate being dissolved in a common solvent (e.g. water) and theresultant solution, spray dried using a spray dryer.

The term “physical mix” or “physical mixture” is a mixture prepared byblending the components (varenicline tartrate and maltodextrin) in ablender. The blending typically takes place by diffusion mechanism.

The term “Powder Transfer System” or “PTS” is a method commonly used formaterial transfers in chemical processes. Pharmaceutical and chemicalplant explosions are industrial disasters with destructive consequences.Charging a reactor with dusty bulk materials is one of the main causesof explosions within the realms of powder handling. Reactors oftencontain solvents into which the reactants are added. The formation of anexplosive atmosphere, which can build up with flammable solvent vaporsand a dust/air mixture of the powder, together with a potential sourceof ignition, have in the past provoked violent explosions, ripping apartwhole facilities. Such risks can be effectively mitigated with the useof a PTS (Powder Transfer System®). It is a patented technology by theDec Group (Dietrich Engineering Consultants). The PTS system is aneffective method for transferring dry and moist powders. It transferspowder in dense-phase (plug flow), i.e., at low velocities, thusavoiding too much energy to form electrostatic discharge within theproduct. Another benefit is that it isolates the receiving vessel duringthe powder charging process by separating the air from the powder thuskeeping the reactor inert. The PTS safely and automatically introducesexplosive, toxic or any other kind of powder to pressurized vessels orto reactors that contain hazardous vapors. The system is usuallyinstalled directly onto the process equipment to be charged. By usingvacuum, the powder gets drawn into the PTS pump body. The flatfiltration membrane isolates the powder from entering into the vacuumline. When the chamber is filled, the product is discharged into thevessel by means of pressurized gas, often nitrogen or another inert gas.At the same time, the reverse flow of the gas cleans the membrane eachtime the product is discharged into the reactor reinstating optimalperformance conditions for the next suction cycle. The overpressure inthe chamber also prevents vapors that are present in the vessel fromentering into the PTS body. The transfer rate is easily controlled bythe pneumatic control panel. The Powder Transfer System empties or fillsall process equipment including reactors, dryers and centrifuges;transfers all powders regardless of their characteristics (sticky, fine,non-free flowing, hygroscopic, moist, etc.); safely conveys toxic<1μg/m³ or dust explosive powders<1 mJ; charges directly into closedvessels under vacuum or pressure; prevents dust creation; eliminatesoxygen from the powder before entering into the process; and charges inthe presence of solvents.

The terms “subject” or “patient” is used interchangeably herein andrefers to a human or other mammal.

The term “therapeutically effective amount,” as used herein, refers tothe amount of varenicline necessary to achieve the desired biologicalresult.

The terms “substantially pure,” or “substantially free of impurities” asused herein refers to the varenicline compound, salt or derivativethereof disclosed herein having less than 150 ppm ofN-nitroso-varenicline per 1 mg of varenicline free base present asmeasured by the LC-ESI-HRMS Method for the Determination of VareniclineNitroso-Drug Substance Related Impurity, U.S. FDA, Aug. 6, 2021,https://www.fda.gov/media/151470/download (accessed Feb. 27, 2022);HPLC; or LCMS.

“Varenicline N-Glucoside” is(8-β-D-Glucopyranosyl-7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine).

B. INTRODUCTION

The present disclosure relates to the field of synthesizing vareniclineand its intermediates. It also relates to varenicline compound that issubstantially free of impurities, such as nitrosamines. The disclosurefurther relates to pharmaceutical compositions comprising varenicline,salt of derivative, and to methods for using such compositions forsmoking cessation or other disorders.

C. PROCESS FOR MAKING VARENICLINE

Generally, there are four stages in the synthetic procedure ofvarenicline tartrate that results in the active pharmaceuticalingredient (“API”) that is substantially free of impurities:

-   -   Stage I: Preparation of        1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone        (“Diamino”)    -   Stage II: Preparation of        1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone        (“Quinoxaline”)    -   Stage III: Preparation of purified        7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine        (“Purified Varenicline Free Base”)    -   Stage IV: Preparation of        7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]        benzazepine,(2R,3R)-2,3-dihydroxy butanedioate. Maltodextrin        (“Varenicline Tartrate Maltodextrin Premix (1:10)”)

Each stage is detailed below.

Stage I: Preparation of 1-(4,5-Diamino-10-Aza Tricyclo[6.3.1.0^(2,7)]Dodeca-2(7),3,5-Trien-10-YL)-2,2,2-Trifluoro-Ethanone

In one embodiment,1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is formed reacting a reducing agent with1-(4,5-Dinitro-10-aza-tricyclo[6.310^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(KSM) in a solvent under hydrogen gas pressure. The reaction isconducted under at a temperature from about 20° C. to about 50° C. Aftera reaction time from about 30 minutes to about 5 hours, the reactionmass is filtered and solvent is distilled off The product isprecipitated by the addition of hexane, isolated by filtration andwashed with hexane. The percentage yield [Percentage Yield=(AchievedYieldx100)/Theoretical Yield] is from about 50% to about 100%.

In another embodiment, the reducing agent used in the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is selected from (a) nickel catalysts such as reducednickel, nickel oxide, Raney nickel and the like; with hydrogen gas orwith reagents which can generate hydrogen during the reaction; (b)platinum catalysts such as platinum plate, platinum sponge, platinumblack, colloidal platinum, platinum oxide, platinum wire and the like;(c) palladium catalysts such as palladium sponge, palladium black,palladium oxide, palladium on carbon, palladium hydroxide on carbon,colloidal palladium, palladium on barium sulfate, palladium on bariumcarbonate; (d) metal hydrides such as sodium borohydride, lithiumborohydride, lithium aluminum borohydride, substituted form of metalhydrides etc., with or without combination of other regents liketrimethyl silyl chloride; (e) sulfides like ammonium sulfide, hydrogensulfide; (f) metal salts like samarium di-iodide.

In one specific embodiment, the reducing agent used in the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is palladium on carbon with hydrogen gas. In anotherembodiment, the pressure of the hydrogen gas varies between 1.0 kg/cm²and 10.0 kg/cm².

In one embodiment, the temperature during the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is from about 20° C. to about 50° C., from about 25°C. to about 45° C., or from about 30° C. to about 40° C. In one specificembodiment, the temperature during the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is about 20° C., about 21° C., about 22° C., about 23°C., about 24° C., about 25° C., about 26° C., about 27° C., about 28°C., about 29° C., about 30° C., about 31° C., about 32° C., about 33°C., about 34° C., about 35° C., about 36° C., about 37° C., about 38°C., about 39° C., about 40° C., about 41° C., about 42° C., about 43°C., about 44° C., about 45° C., about 46° C., about 47° C., about 48°C., about 49° C., or about 50° C.

In another embodiment, the reaction time for the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is from about 30 minutes to about 5 hours, from about45 minutes to about 4 hours, from about 1 hour to about 3 hours, or fromabout 1 hour to about 2 hours. In one specific embodiment, the reactiontime for the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is about 30 minutes, about 45 minutes, about 60minutes, about 75 minutes, about 90 minutes, about 105 minutes, about120 minutes, about 135 minutes, about 150 minutes, about 165 minutes,about 180 minutes, about 195 minutes, about 210 minutes, about 225minutes, about 240 minutes, about 255 minutes, about 270 minutes, about285 minutes, or about 300 minutes. In one embodiment, the solvent in thesynthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is selected from alcohol like methanol, ethanol,isopropyl alcohol and n-propanol; halogenated solvents such asdichloromethane, chloroform and carbon tetrachloride; esters such asethyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate andt-butyl acetate; ether solvents such as tetrahydrofuran and 1,4-dioxane;nitrile solvents such as acetonitrile and propionitrile;dimethylsulfoxide (DMSO); N,N-dimethylformamide (DMF);NN-dimethylacetamide; water; and mixtures thereof

In one embodiment, the solvent in the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is methanol.

In another embodiment, the filtration of the reaction mass of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0²⁷]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is done using gravity filtration, hot filtration, coldfiltration, granular media filtration, mechanical filtration,centrifugal filtration or vacuum filtration. In yet another embodiment,the filtration of the reaction mass of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is done using Sparkler filter, leaf filter, ANFDfollowed by Nutche filtration for final isolation material. In yetanother embodiment, the solvent used during the synthesis of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0²⁷]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is removed by distillation, co-distillation, orco-precipitation. In one embodiment, the solvent used is selected from(a) alcohol like methanol, ethanol, isopropyl alcohol, n-propanol; (b)anti-solvents as ether solvents such as diethyl ether, dimethyl ether,diisopropyl ether and, methyl t-butyl ether; (c) hydrocarbon solventssuch as toluene, xylene, n-heptane, cyclohexane and n-hexane; (d) water;or (e) mixtures thereof. In one embodiment, the1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is precipitated from the reaction mixture usingsolvents such as ether solvents like diethyl ether, dimethyl ether,diisopropyl ether, methyl t-butyl ether; hydrocarbon solvents such astoluene, xylene, n-heptane, cyclohexane and n-hexane; water; andmixtures thereof. In one specific embodiment, the1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is precipitated from the reaction mixture usingdiisopropyl ether or hexane.

In another embodiment, the percentage yield of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is from about 50% to about 100%, from about 55% toabout 99%, from about 60% to about 98%, from about 65% to about 87%, orfrom about 72.28% to about 96.38%. In one specific embodiment, thepercentage yield of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is about 50%, about 55%, about 60%, about 65%, about70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%,about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%,about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about96%, about 97%, about 98%, about 99%, or about 100%.

In yet another embodiment, the purity of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is from about 50% to about 100% as measured by columnchromatography, paper chromatography, thin-layer chromatography, liquidchromatography (LC), affinity chromatography, ion exchangechromatography, size-exclusion chromatography, reversed-phasechromatography, high performance liquid chromatography (HPLC), liquidchromatography-mass spectrometry (LCMS), titration, nuclear magneticresonance (NMR) or Liquid Chromatography-High Resolution MassSpectrometry (LC-ESI-HRMS). In one specific embodiment, purity of1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is about 50%, about 55%, about 60%, about 65%, about70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%,about 77%, about 78%, about 79%, about 80%, about 81%, about 82%, about83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%,about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about96%, about 97%, about 98%, about 99%, or about 100% as measured bycolumn chromatography, paper chromatography, thin-layer chromatography,liquid chromatography, affinity chromatography, ion exchangechromatography, size-exclusion chromatography, reversed-phasechromatography, HPLC, titration, NMR, LCMS or LC-ESI-HRMS.

In one embodiment,1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Stage I-Diamino) is formed by reacting 10% Palladium on carbon andmethanol with1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(KSM) under hydrogen gas pressure. The reaction is conducted under at30-40° C. After 1-2 hours, the reaction mass is filtered and methanol isdistilled off The product is precipitated by the addition of hexane,isolated by filtration and washed with hexane. The percentage yield[Percentage Yield =(Achieved Yieldx100)/Theoretical Yield] is about from72.28 to about 96.38%. A summary of this stage is provided in Table 1.

TABLE 1 Stage-01 in the Process of the Formation of Varenicline TartrateMaltodextrin Premix (1:10) Scheme

Reagents 1. 10% Palladium on carbon 2. Methanol 3. Hydrogen gas 4.Hexane Reaction conditions Temperature: 30-40° C. Time: 1-2 hoursWork-up Filtration of reaction mass, followed by distillation ofmethanol. Precipitation & Precipitation by the addition of Hexane.Product Isolation by Isolation filtration followed by hexane wash. Yield0.7-0.82 X

Stage II: Preparation of 1-(5,8,14-Triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]Hexadeca-2(11),3,5,7,9-Pentaene)-2,2,2-Trifluoro-Ethanone

In another embodiment, Glyoxal solution in water, a catalyst and asolvent are added to1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Diamino) to form1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone (Stage II-Quinoxaline).The reaction is conducted under at a temperature from about 30° C. toabout 80° C. After a reaction time from about 30 minutes to about 5hours, the product is extracted. The product is then precipitated,filtered and washed with a liquid. The product is then purified. Thepercentage yield is from about 30% to about 80%.

In one specific embodiment, the catalyst used in the synthesis of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is sodium bisulfate, ion exchange resin likeAmberlite IRA 67 and similar resins, or mixtures thereof.

In one embodiment, the temperature during the synthesis of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is from about 30° C. to about 80° C., from about35° C. to about 75° C., from about 40° C. to about 70° C., from about45° C. to about 65° C., or from about 55° C. to about 60° C. In onespecific embodiment, the temperature during the synthesis of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is about 30° C., about 35° C., about 40° C.,about 45° C., about 50° C., about 51° C., about 51° C., about 53° C.,about 54° C., about 55° C., about 56° C., about 57° C., about 58° C.,about 59° C., about 60° C., about 61° C., about 62° C., about 63° C.,about 64° C., about 65° C., about 70° C., about 75° C., or about 80° C.

In another embodiment, the reaction time for the synthesis of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is from about 30 minutes to about 5 hours, fromabout 1 hour to about 4 hours, or from about 2 hour to about 3 hours. Inone specific embodiment, the reaction time for the synthesis of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is about 30 minutes, about 45 minutes, about 60minutes, about 75 minutes, about 90 minutes, about 105 minutes, about120 minutes, about 135 minutes, about 150 minutes, about 165 minutes,about 180 minutes, about 195 minutes, about 210 minutes, about 225minutes, about 240 minutes, about 255 minutes, about 270 minutes, about285 minutes, or about 300 minutes.

In yet another embodiment, the pH during the synthesis of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is from about 8.0 to about 14.0.

The cyclization reaction in the synthesis of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is carried out in a solvent selected from wateror other aqueous polar solvents such as aqueous mixture of methanol,ethanol, isopropyl alcohol, tetrahydrofuran, dioxane, tetrahydrofuran,dimethylformamide and dimethylsulfoxide at a temperature of about 10° C.to about 100° C.

In another embodiment, the precipitation of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is done using water, ketones like acetone, andother water miscible solvents.

In yet another embodiment, after precipitation,1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is washed with water to remove inorganicmaterials from the product, and then with non-polar organic solventssuch as hydrocarbons to remove water and other impurities.

In one embodiment,1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is purified by recrystallization using an alcohollike methanol, ethanol and isopropyl alcohol; or other organic solventlike ether and hydrocarbon.

In another embodiment, the percentage yield of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is from about 30% to about 100%, from about 35%to about 90%, from about 40% to about 80%, or from about 46% to about70%. In one specific embodiment, the percentage yield of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is about 30%, about 35%, about 40%, about 45%,about 46%, about 47%, about 48%, about 49%, about 50%, about 51%, about52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%,about 59%, about 60%, about 61%, about 62%, about 63%, about 64%, about65%, about 66%, about 67%, about 68%, about 69%, about 70%, about 75%,about 80%, about 90%, about 95%, or about 100%.

In yet another embodiment, the purity of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is from about 50% to about 100% as measured byHPLC, LCMS, titration, NMR, column chromatography, paper chromatography,thin-layer chromatography, liquid chromatography, affinitychromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, or LC-ESI-HRMS. In onespecific embodiment, purity of1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) is about 50%, about 55%, about 60%, about 65%,about 70%, about 71%, about 72%, about 73%, about 74%, about 75%, about76%, about 77%, about 78%, about 79%, about 80%, about 81%, about 82%,about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%,about 96%, about 97%, about 98%, about 99%, or about 100% as measured byHPLC, LCMS, titration, NMR, column chromatography, paper chromatography,thin-layer chromatography, liquid chromatography, affinitychromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, or LC-ESI-HRMS.

In another embodiment, Glyoxal 40% solution in water, sodium bisulfateand methanol are added to1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Diamino) to form1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline). The reaction is conducted under at 55-60° C.After 2-3 hours, water is added to the reaction mass. The reaction massis then filtered and washed with water. The product is recrystallizedusing methanol. The percentage yield [percentage yield=(AchievedYieldx100)/Theoretical Yield] is from about 46.29% to about 69.44%. Asummary of this stage is provided in Table 2.

TABLE 2 Stage-02 in the Process of the Formation of Varenicline TartrateMaltodextrin Premix (1:10) Scheme

Reagents 1. Glyoxal 40% solution in water 2. Sodium bisulfite 3.Methanol 4. Water Reaction conditions Temperature: 55-60° C. Time: 2-3hours Work-up Addition of water to the reaction mass Precipitation &Filtration followed by water wash Isolation PurificationRecrystallization using methanol. No second crop isolation Yield 0.7-0.9X

Stage III: Preparation of Purified 7,8,9,10-Tetrahydro-6,10-Methano-6H-Pyrazino[2,3-H][3]Benzazepine

In yet another embodiment, sodium carbonate solution and methanol areadded to1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone (Stage II-Quinoxaline) to form crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base). The reaction is conducted at 50-90° C.After a reaction time from about 1 hour to 5 hours, the reaction mass iscooled and filtered. The filtrate is then distilled. Sodium chloridesolution is added and the product is extracted with an extraction agentand washed with sodium chloride solution. Sodium chloride is used forsaturation purposes. Other non-reactive water soluble inorganic saltscan be used for saturation of water. The product is then treated withactivated carbon, washed with methylene dichloride and the methylenedichloride is filtered through a hyflo bed. The solvent (methylenedichloride) is distilled out. A co-distillation is next performed. Theproduct (Semi Dried Material A or raw) is then precipitated and filteredoff.

In one specific embodiment, crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) is purified by acid-base treatment toremove nitrosamine impurities. The Semi Dried Material A (crude StageIII-Varenicline Free Base) is dissolved in methylene chloride and thenan acid is added for salt formation. The organic layer is washed and theproduct is extracted from the aqueous layer. The solvent is distilledand then co-distilled. The Percentage Yield is about from 10% to about100%.

In one embodiment, the temperature during the synthesis of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3]benzazepine(crude Stage III-Varenicline Free Base) is from about 50° C. to about90° C., from about 55° C. to about 80° C., from about 60° C. to about75° C., or from about 64° C. to about 70° C. In one specific embodiment,the temperature during the synthesis of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3 ]benzazepine(crude Stage III-Varenicline Free Base) is about 50° C., about 55° C.,about 60° C., about 61° C., about 62° C., about 63° C., about 64° C.,about 65° C., about 66° C., about 67° C., about 68° C., about 69° C.,about 70° C., about 75° C., about 80° C., about 85° C., or about 90° C.

In another embodiment, the reaction time for the synthesis of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3]benzazepine(crude Stage III-Varenicline Free Base) is from about 30 minutes toabout 5 hours, from about 1 hour to about 4 hours, or from about 2 hourto about 3 hours. In one specific embodiment, the reaction time for thesynthesis of crude 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3 ]benzazepine (crude Stage III-Varenicline Free Base) is about30 minutes, about 45 minutes, about 60 minutes, about 75 minutes, about90 minutes, about 105 minutes, about 120 minutes, about 135 minutes,about 150 minutes, about 165 minutes, about 180 minutes, about 195minutes, about 210 minutes, about 225 minutes, about 240 minutes, about255 minutes, about 270 minutes, about 285 minutes, or about 300 minutes.

In yet another embodiment, the pH during the synthesis of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3]benzazepine(crude Stage III-Varenicline Free Base) is from about 8.0 to 14.0.

In one embodiment, the extraction agent used to extract crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) is a chlorinated solvent such asmethylene chloride or chloroform.

In another embodiment, the precipitation of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) is done using (a) higher alcohol (C3and above) like isopropyl alcohol, n-propanol; (b) anti-solvents asether solvents such as diethyl ether, dimethyl ether, diisopropyl ether,methyl t-butyl ether, tetrahydrofuran and 1,4-dioxane; (c) hydrocarbonsolvents such as toluene, xylene, n-heptane, cyclohexane, hexanes andn-hexane; (d) esters such as ethyl acetate, n-propyl acetate, n-butylacetate, isobutyl acetate and t-butyl acetate; or (e) ketone such asacetone, ethyl methyl ketone methyl isobutyl ketone and mixture ofketone with water.

In one embodiment, crude 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crude Stage III-Varenicline Free Base) ispurified to remove impurities.

A total of 17 impurities are controlled in the Varenicline Free base(Stage III) synthetic process. These impurities are process relatedimpurities. Among these process related impurities, some of theimpurities are identified as potential Genotoxic Impurities andcontrolled with the limit of NMT 0.0426% w/w. All othervarenicline-related compounds are controlled with the limit of not morethan (NMT) 0.15% as per ICH Q3A.

In one specific embodiment, the crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) is purified to substantially removevarenicline nitrosamine impurities, process-related impurities, or acombination thereof.

In another specific embodiment, crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) is purified by (a) acid-base treatmentusing organic and inorganic acids having pKa between 2.0 and 6.0 such astartaric acid, succinic acid, maleic acid, fumeric acid, etc. (b)recrystallization using various solvents, (c) chromatographypurification techniques like column chromatography, preparative HPLC andother equivalent techniques; or (d) reduction/hydrogenation to removenitrosamine impurities.

In one embodiment, the acid used in acid-base treatment of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) is any acid or organic acid. In onespecific embodiment, the acid used in acid-base treatment of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3 ]benzazepine(crude Stage III-Varenicline Free Base) is L(+) Tartaric acid, succinicacid, citric acid, maleic acid, or a combination thereof.

In one specific embodiment, the purification of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) results in the elimination ofnitrosamine impurities. In another embodiment, the purification of crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3 ]benzazepine(crude Stage III-Varenicline Free Base) results in the elimination of100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%,99.0%, 98%, 97%, 96%, or 95% of nitrosamine impurities to form purified7,8,9,10-Tetrahydro-6,10-methano -6H-pyrazino [2,3-h][3]benzazepine(Stage III-Varenicline Free Base).

In another embodiment, the percentage yield of purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (StageIII-Varenicline Free Base) is from about 10% to about 100%, from about20% to about 90%, from about 28.98 to about 86.95%, from about 40% toabout 80%, or from about 50% to about 70%. In one specific embodiment,the percentage yield of purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3]benzazepine(Stage III-Varenicline Free Base) is about 10%, about 20%, about 29%,about 30%, about 35%, about 40%, about 45%, about 50%, about 51%, about52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%,about 59%, about 60%, about 61%, about 62%, about 63%, about 64%, about65%, about 66%, about 67%, about 68%, about 69%, about 70%, about 75%,about 80%, about 87%, about 90%, about 95%, or about 100%.

In yet another embodiment, purified17,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine(Stage III-Varenicline Free Base) is from about 50% to about 100% pureas measured by HPLC, titration, NMR, LCMS, column chromatography, paperchromatography, thin-layer chromatography, liquid chromatography,affinity chromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, or LC-ESI-HRMS. In onespecific embodiment, purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (StageIII-Varenicline Free Base) is about 50%, about 55%, about 60%, about65%, about 70%, about 71%, about 72%, about 73%, about 74%, about 75%,about 76%, about 77%, about 78%, about 79%, about 80%, about 81%, about82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%,about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about95%, about 96%, about 97%, about 98%, about 99%, or about 100% pure asmeasured by HPLC, titration, NMR, LCMS, column chromatography, paperchromatography, thin-layer chromatography, liquid chromatography,affinity chromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, or LC-ESI-HRMS. In yetanother specific embodiment, purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (StageIII-Varenicline Free Base) is at least about 95%, at least about 96%, atleast about 97%, at least about 98%, at least about 99%, at least about99.1%, at least about 99.2%, at least about 99.3%, at least about 99.4%,at least about 99.5%, at least about 99.6%, at least about 99.7%, atleast about 99.8%, or at least about 99.9% pure as measured by HPLC,LCMS, column chromatography, paper chromatography, thin-layerchromatography, liquid chromatography, affinity chromatography, ionexchange chromatography, size-exclusion chromatography, reversed-phasechromatography, titration, NMR, or LC-ESI-HRMS.

In one specific embodiment, sodium carbonate solution and methanol areadded to1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Stage II-Quinoxaline) to form crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base). The reaction is conducted at 64-70° C.After 3 hours, the reaction mass is cooled and filtered. The filtrate isthen distilled. Sodium chloride solution is added and the product isextracted with methylene chloride and washed with sodium chloridesolution. The product is then treated with activated carbon, washed withmethylene dichloride and the methylene dichloride is filtered through ahyflo bed. The solvent (methylene dichloride) is distilled out. Aco-distillation with tertiary butyl methyl ether is next performed. Theproduct (Semi Dried Material A) is precipitated by the addition oftertiary butyl methyl ether and filtered off.

In another specific embodiment, crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine (crudeStage III-Varenicline Free Base) is purified. The reagents used in thepurification process are: sodium chloride, and tertiary Butyl Methylether. The crude 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3]benzazepine is purified by acid-base treatment to remove nitrosamineimpurities. The crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine isdissolved in methylene chloride and then L (+) Tartaric acid solution isadded for salt formation. The solution is stirred and allowed to settlefor layer separation. The aqueous layer is washed with sodium carbonatesolution and the product is extracted from the aqueous layer withmethylene dichloride. Sodium chloride solution is then added to theorganic layer that contains the product and the bottom organic layer isseparated. Methylene dichloride is distilled out of the organic layer.This step is followed by co-distillation with tertiary butyl methylether. The product (purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine) isprecipitated by the addition of tertiary butyl methyl ether and isisolation by filtration followed by tertiary butyl methyl ether washing.The Percentage Yield is about from 28.98 to about 86.95%. A summary ofthe purification of the Varenicline Fee Base is provided in Table 3 anda summary of the purification of Varenicline Free Base is provided inFIG. 1.

TABLE 3 Stage-03 in the Process of the Formation of Varenicline TartrateMaltodextrin Premix (1:10) Scheme

Reagents 1. Sodium carbonate 2. Methanol 3. Methylene dichloride 4.Tertiary Butyl Methyl ether 5. Purified water 6. Sodium chloride7.Activated carbon 8.Hyflo Reaction conditions Temperature: 64-70° C.Time: 3 hours Work-up Cooling & filtration followed by distillation offiltrate. Addition of sodium chloride solution, extraction withmethylene chloride followed by sodium chloride solution washing and thenactivated carbon treatment, solvent distillation followed byco-distillation with Tertiary Butyl Methyl ether Precipitation &Precipitation by the addition of Tertiary Butyl Methyl ether. IsolationProduct isolation by filtration followed by Tertiary Butyl Methyl ether.Purification-For removal of Nitrosamine Impurities Scheme

Reagents 1. Methylene dichloride 2. Sodium chloride 3. L(+)Tartaric acid4. Purified water 5. Sodium carbonate 6. Tertiary Butyl Methyl etherWork-up Purification by acid-base treatment to remove nitrosamineimpurities: Process: Semi dried material dissolved in methylene chlorideand then add L (+) Tartaric acid solution. Stirring settling and layerseparation. Wash the organic layer with sodium carbonate solution.Extract the product from aqueous layer with methylene chloride. Solventdistillation followed by co-distillation with Tertiary Butyl Methylether. Precipitation & Precipitation by the addition of Tertiary ButylMethyl ether. Isolation Product isolation by filtration followed byTertiary Butyl Methyl ether. Yield 0.2-0.60 X

Stage IV: Preparation of7,8,9,10-Tetrahydro-6,10-Methano-6H-Pyrazino[2,3-H][3]Benzazepine,(2R,3R)-2,3-Dihydroxy Butanedioate. Maltodextrin

In one embodiment, Varenicline Tartrate Maltodextrin Premix (1:10) isformed by mixing purified 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3 ]benzazepine with L-(+) tartaric acid, maltodextrin, methanoland water. The mixture is maintained at a temperature from about 20° C.to about 50° C. After 30 minutes, the product is filtered off,precipitated and isolated. The percentage yield is from about 20% toabout 100%.

In one embodiment, 7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3] benzazepine,(2r,3r)-2,3-dihydroxy butanedioate andmaltodextrin are mixed in a weight/weight ratio of 1:10 (i.e.varenicline tartrate 1X and maltodextrin 10X).

In another embodiment, the mixture in Stage IV is maintained at atemperature from about 20° C. to about 50° C., from about 25° C. toabout 45° C., or from about 25° C. to about 35° C. In one specificembodiment, the mixture is maintained at a temperature of about 20° C.,about 21° C., about 22° C., about 23° C., about 24° C., about 25° C.,about 26° C., about 27° C., about 28° C., about 29° C., about 30° C.,about 31° C., about 32° C., about 33° C., about 34° C., about 35° C.,about 36° C., about 37° C., about 38° C., about 39° C., about 40° C.,about 41° C., about 42° C., about 43° C., about 44° C., about 45° C.,about 46° C., about 47° C., about 48° C., about 49° C., or about 50° C.

In yet another embodiment, the product in Stage IV is filtered off usingmicro-filtration, using a cartridge filter, or using a candle filter.

In one embodiment, the percentage yield of Varenicline TartrateMaltodextrin Premix (1:10) is from about 20% to about 100%, from about30% to about 90%, from about 43% to about 96%, from about 40% to about80%, or from about 50% to about 70%. In one specific embodiment, thepercentage yield of Varenicline Tartrate Maltodextrin Premix (1:10) isabout 10%, about 20%, about 30%, about 35%, about 40%, about 42%, about43%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%,about 75%, about 80%, about 85%, about 90%, about 95%, about 96%, orabout 100%.

In another embodiment, Varenicline Tartrate Maltodextrin Premix (1:10)is isolated by spray drying. In yet another embodiment, the duration ofthe spray drying operation is from about 1 hour to about 30 hours, fromabout 3 hours to about 27 hours, from about 6 hours to about 24 hours,from about 9 hours to about 21 hours, from about 10 hours to about 18hours, or from about 11 hours to about 14 hours. In one specificembodiment, the duration of the spray drying operation is about 1 hour,about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours,about 11 hours, about 12 hours, about 13 hours, about 14 hours, about 15hours, about 16 hours, about 17 hours, about 18 hours, about 19 hours,about 20, about 25 hours, or about 30 hours.

In yet another embodiment, the temperature during the spray dryingoperation is from about 20° C. to about 50° C., from about 25° C. toabout 45° C., or from about 30° C. to about 40° C. In one specificembodiment, the temperature during the spray drying operation is about20° C., about 21° C., about 22° C., about 23° C., about 24° C., about25° C., about 26° C., about 27° C., about 28° C., about 29° C., about30° C., about 31° C., about 32° C., about 33° C., about 34° C., about35° C., about 36° C., about 37° C., about 38° C., about 39° C., about40° C., about 41° C., about 42° C., about 43° C., about 44° C., about45° C., about 46° C., about 47° C., about 48° C., about 49° C., or about50° C.

In one embodiment, the inlet temperature of the spray dryer used duringthe spray drying operation is from about 100° C. to about 180° C., fromabout 105° C. to about 170° C., from about 110° C. to about 160° C.,from about 120° C. to about 150° C., or from about 115° C. to about 150°C. In one specific embodiment, the inlet temperature of the spray dryerused during the spray drying operation is about 100° C., about 105° C.,about 110° C., about 115° C., about 120° C., about 125° C., about 130°C., about 135° C., about 140° C., about 145° C., about 150° C., about155° C., about 160° C., about 165° C., about 170° C., about 175° C., orabout 180° C.

In one embodiment, the ID Blower (Induced Draft Fan Blower) flow rate ofthe spray dryer during the spray drying operation is from about 500NM³/hr to about 1000 NM³/hr, from about 600 NM³/hr to about 900 NM³/hr,or from about 700 NM³/hr to about 800 NM³/hr. In one specificembodiment, the ID Blower flow rate of the spray dryer during the spraydrying operation is about 500 NM³/hr, about 550 NM³/hr, about 600NM³/hr, about 650 NM³/hr, about 700 NM³/hr, about 750 NM³/hr, about 800NM³/hr, about 850 NM³/hr, about 900 NM³/hr, about 950 NM³/hr, or about1000 NM³/hr.

In one embodiment, the FD Blower (Forced Draft Fan Blower) flow rate ofthe spray dryer during the spray drying operation is from about 100NM³/hr to about 700 NM³/hr, from about 200 NM³/hr to about 600 NM³/hr,or from about 300 NM³/hr to about 500 NM³/hr. In one specificembodiment, the FD Blower flow rate of the spray dryer during the spraydrying operation is about 100 NM³/hr, about 150 NM³/hr, about 200NM³/hr, about 250 NM³/hr, about 300 NM³/hr, about 350 NM³/hr, about 400NM³/hr, about 450 NM³/hr, about 500 NM³/hr, about 550 NM³/hr, about 600NM³/hr, about 650 NM³/hr, or about 700 NM³/hr.

The ID Blower and FD Blower are part of spray dryer and used tocirculate/create positive air pressure in the system.

In another embodiment, the atomization pressure of the spray dryerduring the spray drying operation is from about 1 kg/cm² to about 10kg/cm², from about 1.5 kg/cm² to about 8 kg/cm², from about 2 kg/cm² toabout 6 kg/cm², or from about 3 kg/cm² to about 4.2 kg/cm². In onespecific embodiment, the atomization pressure of the spray dryer duringthe spray drying operation is about 1 kg/cm², about 1.5 kg/cm², about 2kg/cm², about 2.5 kg/cm², about 3 kg/cm², about 3.5 kg/cm², about 4kg/cm², about 4.2 kg/cm², about 4.5 kg/cm², about 5 kg/cm², about 5.5kg/cm² , about 6 kg/cm², about 6.5 kg/cm², about 7 kg/cm², about 7.5kg/cm², about 8 kg/cm², about 8.5 kg/cm², about 9 kg/cm², about 9.5kg/cm², or about 10 kg/cm².

In yet another embodiment, the feed flow rate of the spray dryer duringthe spray drying operation is from about 10 ml/min to about 120 ml/min,from about 20 ml/min to about 100 ml/min or from about 30 ml/min toabout 90 ml/min. In one specific embodiment, the feed flow rate of thespray dryer during the spray drying operation is about 10 ml/min, about20 ml/min, about 30 ml/min, about 40 ml/min, about 50 ml/min, about 60ml/min. about 70 ml/min, about 80 ml/min, about 90 ml/min, about 100ml/min, aboutl 1 ml/min, or about 120 ml/min.

In another embodiment, the spray dried Varenicline Tartrate MaltodextrinPremix (1:10) has a D₉₀ particle size of less than or equal to 500micron, less than or equal to 400 micron, less than or equal to 300micron, less than or equal to 200 micron, less than or equal to 100micron, or less than or equal to 50 micron. In yet another embodiment,the spray dried Varenicline Tartrate Maltodextrin Premix (1:10) has aD90 particle size from about 5 micron to about 50 micron, from about 50micron to about 100 micron, from about 100 micron to about 200 micron,from about 300 micron to about 400 micron, or from about 400 micron toabout 500 micron.

In one specific embodiment, Varenicline Tartrate Maltodextrin Premix(1:10) is formed by mixing purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3 ]benzazepine withL-(+) tartaric acid, maltodextrin, methanol and water. The mixture ismaintained at 30±3° C. After 30 minutes, the product is filtered offusing micro filtration, precipitated and isolated using spray drying.The percentage yield is from about 42.78 to about 96.25%. A summary ofthis stage of the synthetic procedure is provided in Table 4.

TABLE 4 Stage-04 in the Process of the Formation of Varenicline TartrateMaltodextrin Premix (1:10) Scheme

Reagents 1. L-(+) tartaric acid 2. Maltodextrin 3. Methanol 4. WaterReaction conditions Temperature: 30 ± 3° C. Time: 30 min Work-up Micronfiltration Precipitation & Spray drying Isolation Yield 12-18 X

According to the present disclosure, the level of impurities in theVarenicline Tartrate Maltodextrin Premix (1:10) is determined by HPLC,column chromatography, paper chromatography, thin-layer chromatography,liquid chromatography, affinity chromatography, ion exchangechromatography, size-exclusion chromatography, reversed-phasechromatography, titration, NMR, LCMS, or LC-ESI-HRMS.

In another embodiment, the Varenicline Tartrate Maltodextrin Premix(1:10) has about 50 ppm, about 40 ppm, about 30 ppm, about 25 ppm, about24 ppm, about 23 ppm, about 22 ppm, about 21 ppm, about 20 ppm, about 19ppm, about 18.5 ppm, about 17 ppm, about 16 ppm, about 15 ppm, about 14ppm, about 13 ppm, about 12 ppm, about 11 ppm, about 10 ppm, about 9ppm, about 8 ppm, about 7 ppm, about 6 ppm, about 5 ppm, about 4 ppm,about 3 ppm, about 2 ppm, about 1 ppm of nitrosamine impurity asdetermined by an analysis technique. In one embodiment, the analysistechnique is HPLC, titration, NMR, LCMS, column chromatography, paperchromatography, thin-layer chromatography, liquid chromatography,affinity chromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, or LC-ESI-HRMS.

In yet another embodiment, the Varenicline Tartrate Maltodextrin Premix(1:10) has less than about 50 ppm, less than about 40 ppm, less thanabout 30 ppm, less than about 25 ppm, less than about 24 ppm, less thanabout 23 ppm, less than about 22 ppm, less than about 21 ppm, less thanabout 20 ppm, less than about 19 ppm, less than about 18.5 ppm, lessthan about 17 ppm, less than about 16 ppm, less than about 15 ppm, lessthan about 14 ppm, less than about 13 ppm, less than about 12 ppm, lessthan about 11 ppm, less than about 10 ppm, less than about 9 ppm, lessthan about 8 ppm, less than about 7 ppm, less than about 6 ppm, lessthan about 5 ppm, less than about 4 ppm, less than about 3 ppm, lessthan about 2 ppm, less than about 1 ppm of nitrosamine impurity asdetermined by an analysis technique. In one embodiment, the analysistechnique is HPLC, LCMS, column chromatography, paper chromatography,thin-layer chromatography, liquid chromatography, affinitychromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, titration, NMR, orLC-ESI-HRMS.

In another embodiment, the Varenicline Tartrate Maltodextrin Premix(1:10) has about 50 ppm, about 40 ppm, about 30 ppm, about 25 ppm, about24 ppm, about 23 ppm, about 22 ppm, about 21 ppm, about 20 ppm, about 19ppm, about 18.5 ppm, about 17 ppm, about 16 ppm, about 15 ppm, about 14ppm, about 13 ppm, about 12 ppm, about 11 ppm, about 10 ppm, about 9ppm, about 8 ppm, about 7 ppm, about 6 ppm, about 5 ppm, about 4 ppm,about 3 ppm, about 2 ppm, about 1 ppm of nitrosamine impurity asmeasured by HPLC, LCMS, column chromatography, paper chromatography,thin-layer chromatography, liquid chromatography, affinitychromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, titration, NMR, orLC-ESI-HRMS.

In yet another embodiment, the Varenicline Tartrate Maltodextrin Premix(1:10) has less than about 50 ppm, less than about 40 ppm, less thanabout 30 ppm, less than about 25 ppm, less than about 24 ppm, less thanabout 23 ppm, less than about 22 ppm, less than about 21 ppm, less thanabout 20 ppm, less than about 19 ppm, less than about 18.5 ppm, lessthan about 17 ppm, less than about 16 ppm, less than about 15 ppm, lessthan about 14 ppm, less than about 13 ppm, less than about 12 ppm, lessthan about 11 ppm, less than about 10 ppm, less than about 9 ppm, lessthan about 8 ppm, less than about 7 ppm, less than about 6 ppm, lessthan about 5 ppm, less than about 4 ppm, less than about 3 ppm, lessthan about 2 ppm, less than about 1 ppm of nitrosamine impurity asmeasured by HPLC, LCMS, column chromatography, paper chromatography,thin-layer chromatography, liquid chromatography, affinitychromatography, ion exchange chromatography, size-exclusionchromatography, reversed-phase chromatography, titration, NMR, orLC-ESI-HRMS.

D. VARENICLINE COMPOUND

The varenicline produced by the inventive process described herein canbe in the form of L-tartrate salt, D,L-tartrate salt, D-tartrate salt,meso-tartrate salt. Tartaric acid, citric acid, succinic acid, maleicacid, fumeric acid, etc. can be used for the elimination of nitrosamine.The salts are formed in-situ and salts are dissolved in the aqueousphase and the undissolved nitroamine is extracted in an organic solventto eliminate the nitrosamine impurities. Further the aqueous layer isacidified to obtain pure varenicline base. Further, such salt form maybe anhydrous, a hydrate, or a monohydrate. Such forms are suitable forthe administration of a varenicline compound to human subjects havingless than 150 ppm, less than about 125 ppm, less than about 100 ppm,less than about 75 ppm, less than about 50 ppm, less than about 25 ppm,less than about 20 ppm, less than about 19 ppm, less than about 15 ppm,less than about 10 ppm, or less than about 5 ppm ofN-nitroso-varenicline per 1 mg of varenicline free base.

In other embodiments, the varenicline tartrate has about 1 ppm, about 2ppm, about 3 ppm, about 4 ppm, about 5 ppm, about 6 ppm, about 7 ppm,about 8 ppm, about 9 ppm, or about 10 ppm of N-nitroso-varenicline per 1mg of varenicline free base.

The processes described herein can be employed to make various forms ofsubstantially pure varenicline API. The L-tartrate salt exists as threepossible forms: two anhydrous forms and one hydrate form. Of the twoanhydrous forms, Form A and Form B, Form A is the kinetic polymorph,which will convert under appropriate conditions to the thermodynamicallyfavored Form B. The hydrate L-tartrate salt Form C is a monohydrate andis relatively stable under ambient conditions. It will maintain its oneequivalent of water under vacuum at moderate temperatures for at least aday (e.g., for 24 hours in a 45° C. vacuum oven), but eventually overtime (i.e., 48 hours or more) will lose water and convert to theanhydrous Form B. Form B is the most stable of the polymorphs at lowhumidity. Accordingly, Form B would appear to be the most appropriateand most stable polymorph of the L-tartrate salts of5,8,14-triazatetracyclo[10.3.1.02,11.04,9]-hexadeca-2(11),3,5,7,9-pentaenefor pharmaceutical formulation use.

E. IMPURITIES

Three nitrosamine impurities could have formed during the manufacturingprocess of Varenicline Tartrate Maltodextrin premix (1:10) API. Dinitronitrosamine impurity may have formed during the nitration reaction forthe preparation of the 1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(KSM). This impurity is a carryover impurity and converts to Diaminonitrosamine impurity in Stage 1 of Varenicline Tartrate MaltodextrinPremix (1:10) synthetic procedure. This Diamino nitrosamine converts toVarenicline nitrosamine impurity during the subsequent stages. Sinceboth Dinitro nitrosamine and Diamino nitrosamine are carryoverimpurities and convert to Varenicline nitrosamine during themanufacturing process, these dinitro nitroamine and diamino nitrosamineimpurities are controlled in Stage 3 and observed ‘Not detected’ levelin Varenicline free base before purification itself.

A total of 17 impurities are controlled in the Varenicline Free base(Stage III) synthetic process. These impurities are process-relatedimpurities. Among these process-related impurities, some of theimpurities are identified as potential Genotoxic Impurities andcontrolled with the limit of NMT 0.0426% w/w. All othervarenicline-related compounds are controlled with the limit of NMT 0.15%as per ICH Q3A.

Moreover, six process Related/Degradation impurities are controlled invarenicline tartrate maltodextrin premix API with the limit of NMT 0.15%w/w.

Further, three nitrosamine impurities are controlled each in the premixAPI with the limit of NMT 5.26 ppm and total nitrosamines are controlledwith the limit of NMT 7.24 ppm.

This process is efficient in eliminating the nitrosamine impurities fromthe API. The nitrosamine impurities are substantially or completelyeliminated by converting the varenicline base into varenicline salt withan organic or inorganic acid having a pKa between 2 and 6. Because theabsence of basic nitrogen due to the presence of the nitroso groupprevents the nitrosamine impurities to form salt of acids, nitrosamineimpurity fails to dissolve in the aqueous solution, and could beextracted in an organic solvent. Thus, nitrosamine impurities could becompletely removed in this acid-base treatment process.

In one embodiment, the Varenicline Tartrate Maltodextrin Premix (1:10)has not more than about 0.2% w/w, not more than about 0.15% w/w, notmore than about 0.1% w/w, not more than about 0.05% w/w, not more thanabout 0.0438% w/w, not more than about 0.03% w/w, not more than about0.02% w/w, or not more than about 0.01% w/w of impurities such as thoselisted in Tables 5 and 6 below, for example, Varenicline KSM,Varenicline Stage-01, Mononitro Protected compound, Metadinitroprotected compound, Mononitro deprotected, Impurity-G, Meta dinitrodeprotected, Monoamino protected compound, Metadiamino protectedcompound, Impurity-C, Impurity-F, Impurity-D, Amino nitro protected,Amino nitro de-protected, Varenicline Stage-02, Methyl VareniclineProtected, or Methyl Varenicline as determined by an analysis technique.In one embodiment, the analysis technique is HPLC, LCMS, columnchromatography, paper chromatography, thin-layer chromatography, liquidchromatography, affinity chromatography, ion exchange chromatography,size-exclusion chromatography, reversed-phase chromatography, titration,NMR, or LC-ESI-HRMS.

In another embodiment, the Varenicline Tartrate Maltodextrin Premix(1:10) has not more than about 10 ppm, about 9 ppm, about 8 ppm, about 7ppm, about 6 ppm, about 5.26, about 5 ppm, about 4 ppm, about 3 ppm,about 2 ppm, about 1 ppm of Dinitro Nitrosoamine impurity, DiaminoNitrosoamine impurity, or Nitroso Varenicline impurity as determined byan analysis technique. In one embodiment, the analysis technique isHPLC, LCMS, column chromatography, paper chromatography, thin-layerchromatography, liquid chromatography, affinity chromatography, ionexchange chromatography, size-exclusion chromatography, reversed-phasechromatography, titration, NMR, or LC-ESI-HRMS.

A list of the possible impurities is provided in Tables 5 and 6 below.

TABLE 5 Possible Varenicline Impurities in Varenicline base (Stage 3)and Varenicline Tartrate Maltodextrin premix API (Stage 4) Chemical Nameof the S.No Impurity and Testing Method Structure of the Impurity OriginControl Process Related Impurity:  1 Varenicline KSM1-(4,5-Dinitro-10-aza- tricyclo[6.3.1. 0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2- trifluoro-ethanone (RS Method-I)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w.  2Varenicline Stage-01 1-(4,5-diamino-10-aza- tricyclo[6.3.1.0 ^(2,7)]dodeca- 2(7),3,5-trien-10-yl)-2,2,2- trifluoro-ethanone (RS Method-I)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2  3 Varenicline Stage-02 1-(5,8,14-Triazatetracyclo[10.3.1.0^(2,11).0^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluro- ethanone (Quinoxaline) (RS Method-I)

Carry over impurity. This impurity is controlled in Stage-03 with alimit NMT 0.15% w/w.  4 Mononitro Protected compound:7-nitro-3-(trifluoroacetyl)-2,3,4,5- tetrahydro-1H-1,5-methano-3-benzazepine (RS Method-II)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2  5 Metadinitro protected compound:6,8-dinitro-2,3,4,5-tetrahydro-1H 1,5-mcthano-3-benzazepine (RSMethod-II)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 US2013/0030179 A1  6 Mononitro deprotected:7-nitro-2,3,4,5-tetrahydro-1H-1,5- methano-3-benzazepine (RS Method-II)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2  7 Impurity-G: 7,8-Dinitro-2,3,4,5-tetrahydro-1H-1,5-methano-3-benzazepine (RS Method-II)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 US2013/0030179 A1  8 Meta dinitro deprotected:3,5-Dinitro-10-aza- tricyclo[6.3.1.0^(2,7)]dodeca-2,4,6- triene (RSMethod-II)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 US2013/0030179 A1  9 Monoamino protected compound:3-(trifluoroacetyl)-2,3,4,5- tetrahydro-1H-1,5-methano-3-benzazepin-7-amine (RS Method-II)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 10 Metadiamino protected compound:3-(trifluoroacetyl)-2,3,4,5- tetrahydro-1H-1,5-methano-3-benzazepine-6,8-diamine (RS Method-II)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 US2013/0030179 A1 11 Impurity-C:2,3,4,5-tetrahydro-1H-l,5- methano-3-benzazepin-7-amine (RS Method-I)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 12 Impurity-F: 7,8-Diamino-2,3,4,5-tetrahydro-1H-l,5-methano-3-benzazepine (RS Method-I)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 US2013/0030179 A1 13 Impurity-D:2,3,4,5-tetrahydro-1H-1,5- methano-3-benzazepine-6,8- diamine (RSMethod-I)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 US2013/0030179 A1 14 Amino nitro protected:1-(7-Amino-8-nitro-1,2,4,5- tetrahydro-3H,-l,5- methanobenzo[d]azepin-3-yl)- 2,2,2-trifluoroethan-1-one. (Controlled in Stage I)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-03 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 15 Amino nitro de-protected:8-nitro-2,3,4,5-tetrahydro-1H-1,5- methanobenzo [d]azepin-7-Amine(Controlled in Stage I)

Carry over impurity. This is a potential Genotoxic Impurity (GTI)impurity and is controlled in Stage-01 with a limit 0.0438% w/w. Ref:WO2007/110730 A2 16 Methyl Varenicline Protected2-methyl-7,8,9,10-Tetrahydro-8- (trifluoroacetyl)-6,10-methano-6H-pyrazino[2,3- h][3]benzazepine. (or) 2,2,2-T rifluoro-1-(2-methyl-6,7,9,10-tetrahydro-6,10- methano-8H-pyrazino [2,3-h][3]benzazepin-8-yl)ethanone.

Process impurity. Ref: WO2011/110954 A1 17 Methyl Varenicline:2-methyl-7,8,9,10-tetrahydro-6H- 6,10-methanoazepino[4,5-g] quinoxaline(RS Method-I)

Process impurity. This impurity is controlled in stage-3 with a limitNMT 0.15% w/w. Ref: WO2011/110954 A1 Varenicline Tartrate MaltodextrinPremix: Process related/Degradation impurity. 1 Diamide impurity: Bis(7,8,9,10-tetrahydro-6,10- methano-6H-pyrazino[2,3-h][3]-benzazepine)-amide (RS Method-II)

Process impurity. This impurity is controlled in premix APIspecification with a limit NMT 0.15% w/w. 2 Monomethyl Tartrate(Tartaric acid Monomethyl ester) (LCMS-ESI)

Process related/ degradation on impurity. This impurity is controlled infinal premix API specification with a limit NMT 0.15% w/w. 3 DimethylTartrate (Tartaric acid dimethyl ester) (LCMS-APCI)

Process related/ degradation on impurity. This impurity is controlled infinal premix API specification with a limit NMT 0.15% w/w. 4 N-MethylVarenicline: 7,8,9,10-tetrahydro-8-methyl-6,10-Methano-6H-pyrazino[2,3-h] [3]benzazepine (RS Method-III)

Degradation impurity. Controlled in premix API with a limit of NMT 0.15%w/w. 5 N-Formyl Varenicline: 6,7,9,10-Tetrahydro-6,10-methano-8H-pyrazino[2,3- h][3]benzazepine-8- carboxaldehyde (RSMethod-II)

Degradation impurity. Controlled in premix API with a limit of NMT 0.15%w/w. 6 Varenicline N-Glucoside (RS Method-III)

Degradation impurity. Controlled in premix API with a limit of NMT 0.15%w/w.

TABLE 6 Varenicline Nitrosamine Impurities Structure of the S.NoChemical Name of the Impurity Impurity Origin Common Name of theImpurity 7 Dinitro Nitrosoamine impurity: 4,5-Dinitro-10-nitroso-10-aza-tricyclo [6.3.1.0^(2,7)] dodeca-2,4,6- triene. (LCMS Method-I)

Carry over impurity from KSM Controlled final premix API specificationwith a limit NMT 5.26 ppm. 8 Diamino Nitrosoamine impurity:10-nitroso-10-aza-tricyclo[6.3.1. 0^(2,7)]dodeca-2,4,6-triene-4,5-diamine. (LCMS Method-II)

Carry over impurity from stage-1 Controlled in final premix APIspecification with a limit NMT 5.26 ppm. 9 Nitroso Varenicline impurity:7,8,9,10-tetrahydro-8-nitroso-6,10- Methano-6H-pyrazino[2,3-h][3]benzazepine (LCMS Method-I)

Process impurity Controlled in final premix API specification with alimit NMT 5.26 ppm.

F. PHARMACEUTICAL COMPOSITIONS COMPRISING VARENICLINE COMPOUND

The substantially pure L-tartrate, the D-tartrate, the D,L-tartrate andthe meso-tartrate salts of the present disclosure can be administeredvia either the oral, transdermal (e.g., patch), intranasal, sublingual,rectal, parenteral or topical routes. Transdermal and oraladministration are preferred. These salts may be administered in dosagesranging from about 0.01 mg up to about 1500 mg per day, preferably fromabout 0.1 to about 300 mg per day in single or divided doses, althoughvariations will necessarily occur depending upon the weight andcondition of the subject being treated and the particular route ofadministration chosen. However, a dosage level that is in the range ofabout 0.001 mg to about 10 mg per kg of body weight per day is typicallyemployed.

The tartrate salts can be administered alone or in combination withpharmaceutically acceptable carriers or diluents by any of the severalroutes previously indicated. More particularly, the active salts can beadministered in a wide variety of different dosage forms, e.g., they maybe combined with various pharmaceutically acceptable inert carriers inthe form of tablets, capsules, transdermal patches, lozenges, troches,hard candies, powders, sprays, creams, salves, suppositories, jellies,gels, pastes, lotions, ointments, aqueous suspensions, injectablesolutions, elixirs, syrups, and the like. Such carriers include soliddiluents or fillers, sterile aqueous media and various non-toxic organicsolvents. In addition, oral pharmaceutical compositions can be suitablysweetened and/or flavored. In general, the active compound is present insuch dosage forms at concentration levels ranging from about 5.0% toabout 70% by weight.

For oral administration, tablets containing various excipients such asmicrocrystalline cellulose, sodium citrate, calcium carbonate, dicalciumphosphate and glycine may be employed along with various disintegrantssuch as starch (preferably corn, potato or tapioca starch), alginic acidand certain complex silicates, together with granulation binders likepolyvinylpyrrolidone, sucrose, gelatin and acacia. Additionally,lubricating agents such as magnesium stearate, sodium lauryl sulfate andtalc can be used for tableting purposes. Solid compositions of a similartype may also be employed as fillers in gelatin capsules; preferredmaterials in this connection also include lactose or milk sugar, as wellas high molecular weight polyethylene glycols. When aqueous suspensionsand/or elixirs are desired for oral administration the active ingredientmay be combined with various sweetening or flavoring agents, coloringmatter and, if so desired, emulsifying and/or suspending agents,together with such diluents as water, ethanol, propylene glycol,glycerin and various combinations thereof

In one embodiment, a 0.5 mg varenicline tablet contains about 0.85 mgvarenicline tartrate equivalento about 0.5 mg varenicline free base. Inanother embodiment, a 1 mg varenicline tablet contains about 1.7 mgequivalent to about 1 mg varenicline free base.

In a specific embodiment, a tablet comprises:

about 0.85 mg substantially pure varenicline tartrate (equivalent to 0.5mg free base);

about 5-15 mg croscarmellose sodium

about 5-50 mg maltodextrin;

about 100-200 mg microcrystalline cellulose;

about 0.5-2.0 mg stearic acid.

In another specific embodiment, a tablet comprises:

about 1.7 mg substantially pure varenicline tartrate (equivalent to 1 mgfree base);

about 5-15 mg croscarmellose sodium

about 5-50 mg maltodextrin;

about 100-200 mg microcrystalline cellulose;

about 0.5-2.0 mg stearic acid.

The tablets can be film-coated with a coating material containinghydroxypropyl cellulose, hypromellose, talc, and titanium dioxide. Inanother embodiment, the tablets are film-coated with a coating materialcontaining hydroxypropyl cellulose. hypromellose, talc, titaniumdioxide, FD&C blue #2/indigo carmine aluminum lake and iron oxideyellow.

In another embodiment, a tablet comprises substantially pure vareniclinetartrate, microcrystalline cellulose, anhydrous dibasic calciumphosphate, croscarmellose sodium, colloidal silicon dioxide, magnesiumstearate, Opadry® White (for 0.5 mg varenicline free base), Opadry® Blue(for 1 mg varenicline free base), and Opadry® Clear.

G. METHODS OF TREATMENT

The present disclosure further provides a method for treating nicotinedependency, addiction and withdrawal in a subject in need thereof,comprising the administration of a varenicline salt to a human subjecthaving less than 150 ppm, less than about 125 ppm, less than about 100ppm, less than about 75 ppm, less than about 50 ppm, less than about 25ppm, less than about 20 ppm, less than about 15 ppm, less than about 10ppm, or less than about 5 ppm of N-nitroso-varenicline per 1 mg ofvarenicline free base.

In other embodiments, the varenicline tartrate has about 1 ppm, about 2ppm, about 3 ppm, about 4 ppm, about 5 ppm, about 6 ppm, about 7 ppm,about 8 ppm, about 9 ppm, or about 10 ppm of N-nitroso-varenicline per 1mg of varenicline free base.

In another embodiment, there is a method of treatment for nicotinedependency, addiction and withdrawal in a subject in need thereof,comprising the oral administration of a pharmaceutical compositioncomprising substantially pure varenicline tartrate.

In some embodiments, the varenicline is orally administered one weekbefore the date set by the patient to stop smoking. Alternatively, thepatient can begin dosing and then quit smoking between days 8 and 35 oftreatment.

In some embodiments, the recommended dose of varenicline free base is 1mg twice daily following a 1-week titration as detailed in Table 7below.

TABLE 7 Recommended dose of varenicline Days 1-3: 0.5 mg free base oncedaily Days 4-7: 0.5 mg free base twice daily Day 8-end of 1 mg free basetwice treatment: daily

Patients are preferably treated with varenicline for 12 weeks. Forpatients who have successfully stopped smoking at the end of 12 weeks,an additional course of 12 weeks treatment with varenicline isrecommended to further increase the likelihood of long-term abstinence.

In some embodiments, the methods disclosed herein reduce smoking by 50%from baseline within the first four weeks, by an additional 50% in thenext four weeks, and continue reducing with the goal of reachingcomplete abstinence by 12 weeks. The present disclosure also relates toa method of treating nicotine dependency, addiction and withdrawal in asubject in need thereof, comprising providing a pharmaceuticalcomposition comprising about 0.5 mg to about 2 mg substantially purevarenicline tartrate; and orally administering the composition in one ormore daily doses, wherein the subject receives a total of no more thanabout 37 ng of N-nitroso-varenicline impurity per day. In oneembodiment, the composition comprises about 1.7 mg of vareniclinetartrate that has less than 25 ppm of N-nitroso-varenicline impurity asmeasured by the LC-ESI-HRMS Method; HPLC; or LCMS. In anotherembodiment, the composition comprises about 0.85 mg of vareniclinetartrate that has less than 25 ppm of N-nitroso-varenicline impurity asmeasured by the LC-ESI-HRMS Method; HPLC; or LCMS.

Alternatively, the composition comprises about 1.7 mg of vareniclinetartrate that has less than 19 ppm of N-nitroso-varenicline impurity asmeasured by the LC-ESI-HRMS Method, HPLC, or LCMS; or the compositioncomprises about 0.85 mg of varenicline tartrate that has less than 19ppm of N-nitroso-varenicline impurity as measured by the LC-ESI-HRMSMethod, HPLC, or LCMS.

In one embodiment, the compounds, intermediates and pharmaceuticalcompositions of the present disclosure are used for the treatment ofnicotine addiction, inflammatory bowel disease (including but notlimited to ulcerative colitis, pyoderma gangrenosum and Crohn'sdisease), irritable bowel syndrome, spastic dystonia, chronic pain,acute pain, celiac sprue, pouchitis, vasoconstriction, anxiety, panicdisorder, depression, bipolar disorder, autism, sleep disorders, jetlag, amyotrophic lateral sclerosis (ALS), cognitive dysfunction,hypertension, bulimia, anorexia, obesity, cardiac, arrhythmias, gastricacid hypersecretion, ulcers, pheochromocytoma, progressive supranuclearpalsy, chemical dependencies and addictions (e.g., dependencies on, oraddictions to nicotine (and/or tobacco products), alcohol,benzodiazepines, barbiturates, opioids or cocaine), headache, stroke,traumatic brain injury (TBI), obsessive-compulsive disorder, psychosis,Huntington's Chorea, tardive dyskinesia, hyperkinesia, dyslexia,schizophrenia, multi-infarct dementia, age related cognitive decline,epilepsy, including petit mal absence epilepsy, senile dementia of theAlzheimer's type (AD), Parkinson's disease (PD), attention deficithyperactivity disorder (ADHD) and Tourette's Syndrome.

In another embodiment, the compounds, intermediates and pharmaceuticalcompositions of the present disclosure may also be used in combinationwith an antidepressant such as, for example, a tricyclic antidepressantor a serotonin reuptake inhibiting antidepressant (SRI), in order totreat both the cognitive decline and depression associated with AD, PD,stroke, Huntington's Chorea or traumatic brain injury (TBI): incombination with muscarinic agonists in order to stimulate both centralmuscarinic and nicotinic receptors for the treatment, for example, ofALS, cognitive dysfunction, age related cognitive decline, AD, PD,stroke, Huntington's Chorea and TBI; in combination with neurotrophicfactors such as NGF in order to maximize cholinergic enhancement for thetreatment, for example, of ALS, cognitive dysfunction, age relatedcognitive decline, AD, PD stroke, Huntington's Chorea and TBI; or incombination with agents that slow or arrest AD such as cognitionenhancers, amyloid aggregation inhibitors, secretase inhibitors, taukinase inhibitors, neuronal anti-inflammatory agents and estrogen-liketherapy.

H. EXAMPLES

The following examples are included to demonstrate certain embodimentsof the present disclosure. Those of skill in the art should, however, inlight of the present disclosure, appreciate that modifications can bemade in the specific embodiments that are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention. Therefore, all matter set forth is to be interpreted asillustrative and not in a limiting sense.

Examples are provided for the preparation of Varenicline TartrateMaltodextrin premix (1:10) from the KSM,1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoroethanone.Also Examples are provided for demonstrating the purification ofVarenicline base for eliminating nitrosamines and nitrosamine contentresults in Varenicline base before and after purification.

Example 1 Stage I: Preparation of1-(4,5-Diamino-10-Aza-Tricyclo[6.3.1.0^(2,7)]Dodeca-2(7),3,5-Trien-10-YL)-2,2,2-Trifluoro-Ethanone

The following is an illustration of the chemical reaction to produce1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(Diamino) starting from1-(4,5-Dinitro-10-aza-tricyclo[6.310^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(KSM). The synthetic procedure is discussed in details below. Throughoutthis synthetic procedure, X=32.50±2.50 kg of1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone].

Part A

Reactor A and catalyst preparation vessel are pre-cleaned with methanoland dried under vacuum. Into Reactor A, the following materials arecharged in order: 11.50 X kg of methanol and 1.00 X kg of1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(KSM) at a temperature of 30±5° C. The Powder Transfer System (PTS) isflushed with 0.30 X kg of methanol and the flushed methanol istransferred into Reactor A. Next, 1.00 X kg of methanol is added toReactor A through spray nozzle.

Into the catalyst preparation vessel, 0.10 X kg of 10% palladium carbonand 1.00 X kg of methanol are added under nitrogen atmosphere. Thecatalyst slurry is stirred for 10±5 minutes.

The pressure of the mixing vessel is raised to about 1.0 kg/cm² and thecatalyst slurry is transferred from catalyst preparation vessel intoReactor A under nitrogen atmosphere.

1.00 X kg of methanol is charged into the catalyst preparation vesseland the mixture is stirred for 5 minutes. The pressure is raised at 1.0kg/cm² and the methanol is transferred into Reactor A under nitrogenatmosphere. 1.00 X kg of methanol is charged into Reactor A throughspray nozzle.

The reaction mass is stirred at 35±5° C. for 3 hours ±5 minutes underhydrogen pressure of 5.0 to 6.0 kg/cm². Reaction is slightly exothermic.The temperature should not rise to more than 40° C. If temperature goesbeyond 45° C., hydrogen is released and the mass is cooled using chilledwater/chilled brine in the reactor jacket.

To monitor the reaction, a reaction sample is checked for the content of1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(KSM)by HPLC analysis (% area). The test parameters are provided in Table 8.

TABLE 8 Test parameters of the Reaction in Stage 1 Test parameters Limit1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2, 7)]dodeca- Not more than 0.52(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(KSM) Peak 1 at RRT 1.23Not more than 0.5 Peak 2 at RRT 1.30 Not more than 0.5

If reaction sample complies the limit, then the next operation isproceeded with. If reaction sample does not comply the limit, thereaction mass is maintained at a temperature of 35±5° C. and a pressureof 5.0 to 6.0 kg/cm² and a sample is tested at an interval of every 2hours until complies.

The reaction mass is then filtered from Reactor A through the catalystfilter and the clear filtrate is re-circulated back to Reactor A. Thefiltrate from catalyst filter is collected through the cartridge filterA into the mother liquor tank. 3.16 X kg of methanol is then chargedinto Reactor A through spray nozzle. The methanol is filtered fromReactor A through the catalyst filter and the filtrate is transferredthrough cartridge filter A into the mother liquor tank. The filtratefrom the mother liquor tank is transferred and collected in Reactor Bthrough transfer line area under nitrogen atmosphere.

0.35 X kg of methanol is then charged into the mother liquor tank undernitrogen atmosphere. The methanol from the mother liquor tank is thentransferred and collected in Reactor B through transfer line area undernitrogen atmosphere.

80 L of process water is charged into the catalyst preparation vesseland 300 L of process water is charged into the Reactor A through spraynozzle. The water is re-circulated to Reactor A through the catalystfilter. The re-circulated water is drained into the mother liquor tank.

Part B

The reactor (Reactor B/C), Cartridge Filter B, and Centrifuge B arepre-cleaned with methanol and dried under vacuum. The vacuum tray dryeris flushed with hexanes (mixture of isomers) and dried under vacuum. Thedryer is dried under vacuum.

If Reactor B is used, the filtrate from the Mother liquor tank iscollected into Reactor B through Cartridge Filter B under nitrogenatmosphere. If Reactor C is used, the filtrate is collected from motherliquor tank into clean HDPE container through transfer line near ReactorC under nitrogen atmosphere. Approximately half the quantity of filtrateis charged into Reactor C through Cartridge Filter B from HDPE containerunder nitrogen atmosphere.

The methanol is distilled out completely under vacuum not less than 650mmHg and temperature of not more than 45° C. The temperature should notexceed 45° C. and the distillation time should not exceed 15 hours. Thevacuum is released under nitrogen atmosphere and the mass is cooled to30±3° C.

0.34 X kg of hexanes is charged into Reactor B under nitrogen atmosphereand a vacuum of NLT 650 mmHg is applied. The hexanes is completelydistilled out under vacuum NLT 650 mmHg and temperature of NMT 45° C.The vacuum is released under nitrogen atmosphere and the mass is cooledto 30±3° C.

2.62 X kg of Hexanes is charged into Reactors B/C at 30±3° C. undernitrogen atmosphere. The mass is stirred at 30±3° C. for 2 hour ±5minutes and is filtered through the centrifuge B at RPM of 500±50 undernitrogen atmosphere. The centrifuge RPM is raised to 950±50 and thematerial is stir dried. Reactor B is flushed with 0.655 X kg of hexanesunder nitrogen atmosphere.

The wet cake in the centrifuge B at RPM of 500±50 is washed with thehexanes obtained from the previous operation under nitrogen atmosphere.The centrifuge RPM is raised to 950±50 and the material is stir dried.The spin dried material is then charged into the dryer and dried at atemperature of 43±2° C. and under a vacuum of NLT 650 mmHg for 8 hours±5 minutes. The vacuum is then released and the dried material isunloaded and weighed.

YIELD: The expected yield is about 0.60 X to 0.80 X. The percentageyield [Percentage Yield =(Achieved Yieldx100)/Theoretical Yield] isabout from 72.28 to about 96.38%.

Example 2 Stage II: Preparation of1-(5,8,14-Triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]Hexadeca-2(11),3,5,7,9-Pentaene)-2,2,2-Trifluoro-Ethanone

The following is an illustration of the chemical reaction to produce1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.⁴¹]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Quinoxaline) starting from1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone (Diamino). The syntheticprocedure is discussed in details below. Throughout this syntheticprocedure, X=38.00±1.50 kg of varenicline tartrate maltodextrin premix(1:10) Stage-01 (Diamino or “Varenicline Tartrate Maltodextrin Premix(1:10) Stage-01”).

Reactor 2-A and the Vacuum Tray Dryer are flushed with methanol anddried under vacuum. Reactor B/C is flushed with process water and driedunder vacuum. The Glass Dosing Tank and the Centrifuge are cleaned withprocess water. The Cartridge Filter and the Mixing Vessel MV-0101 areflushed with methanol.

PREPARATION OF AQUEOUS GLYOXAL SODIUM BISULFITE SOLUTION: 5.61 X L ofprocess water is charged into Reactor B/C. 0.802 X kg of sodiumbisulfate is added into Reactor B/C under nitrogen atmosphere and 0.56 Xkg of 40% aqueous glyoxal is charged into Reactor B/C at 30±3° C. understirring condition. The clarity of the solution is checked visually. Ifsolution is clear, the next operation is proceeded to. If the solutionis not clear, the solution is stirred at 30±3° C. and the clarity of thesolution is checked every 15 minutes until the solution is clear.

1.58 X kg of methanol is charged into Reactor 2-A under nitrogenatmosphere and 1.00 X kg of Varenicline Tartrate Maltodextrin Premix(1:10) Stage-01 (or diamino) is charged into Reactor 2-A at 30±3° C.2.00 X L of process water is added into Reactor 2-A under nitrogenatmosphere at 30±3° C. The mass is then stirred at 30±3° C. for15±minutes. The mass temperature is raised to 58±2° C. under stirring.

The aqueous glyoxal sodium bisulfite solution is charged in lot wiseinto the Dosing Tank from Reactor B/C by using residual vacuum and thevacuum is released using nitrogen. Once all of the aqueous glyoxalsodium bisulfite solution in Reactor B/C is added into the Dosing Tank,the reactor is flushed with 0.15 X L of process water and the flushedwater is charged into the dosing tank.

The aqueous glyoxal sodium bisulfite solution is slowly added fromDosing Tank to Reactor 2-A at 58±2° C. over a period of 45 minutes. Theflushed water from Dosing Tank is charged into Reactor 2-A. The mass isstirred at 58±2° C. for 3 hours ±5 minutes. The Varenicline TartrateMaltodextrin Premix (1:10) Stage-01 (or diamino) content is checked byHPLC analysis. The Varenicline Tartrate Maltodextrin Premix (1:10)Stage-01 (or diamino) content should be not more than 1.50 (% area). Ifthe content is more than this limit, the reaction mass is maintained at58±2° C. for 2 hours and re-tested at an interval of every 2 hours untilit complies the limit. Once the HPLC sample complies the limit, the massis then cooled to 30±3° C. Then, 10.00 X L of process water is thencharged into Reactor 2-A through charging line at 30±3° C. The mass isstirred at a temperature of 30±3° C. for 1 hour ±5 minutes. If required,the mass is cooled to 27±3° C. The mass is stirred at a temperature of27±3° C. for 1 hour ±5 minutes.

CRUDE-I FILTRATION: The mass obtained from Reactor 2-A is filteredthrough the Centrifuge at RPM of 500±50 under nitrogen atmosphere. TheCentrifuge RPM is raised to 950±50 and the material is spin dried.Reactor 2-A is flushed with 2.00 X L of process water. The wet cake iswashed in the Centrifuge at RPM of 500±50 with the process waterobtained from the previous operation under nitrogen atmosphere. TheCentrifuge RPM is raised to 950±50 and the material is spin dried. TheCentrifuge is stopped and after waiting for 10±2 minutes, the spin driedmaterial is unloaded from the Centrifuge under nitrogen atmosphere.

INTERMITTENT CLEANING: Reactor 2-A is flushed with 10 L of process waterand the flushed water is drained in to strong effluent.

WATER SLURRY WASHING: 7.00 X L of process water is charged into Reactor2-A through charging line. The spin dried material is charged intoReactor 2-A through the manhole under nitrogen atmosphere. The mass isstirred for 10±5 minutes at 27±3° C.

INTERMITTENT CLEANING: The Centrifuge is flushed with 10 L of processwater and the flushed water is drained in to strong effluent.

CRUDE-II FILTRATION: The mass obtained from Reactor 2-A is filteredthrough the Centrifuge at RPM of 500±50 under nitrogen atmosphere. TheCentrifuge RPM is raised to 950±50 and the material is spin dried.Reactor 2-A is flushed with 2.00 X L of process water. The wet cake iswashed in the Centrifuge at RPM of 500±50 with the process waterobtained from the previous operation under nitrogen atmosphere. TheCentrifuge RPM is raised to 950±50 and the material is spin dried at RPMof 950±50. The Centrifuge is stopped. After waiting for 10±2 minutes,the spin dried material is unloaded under nitrogen atmosphere.

INTERMITTENT CLEANING: Reactor 2-A and Reactor B/C are flushed each with10.00 kg of methanol. 5.00 kg of methanol is charged into the GlassDosing Tank using vacuum and the methanol is bounced for three to fourtimes by controlling vacuum. The bounced methanol is drained.

PURIFICATION: 3.00 X kg of methanol is charged into Reactor 2-A undernitrogen atmosphere. The spin dried material is charged into Reactor 2-Aunder stirring at 30±3° C. under nitrogen atmosphere. Reactor 2-A isflushed with 0.95 X kg methanol under nitrogen atmosphere. The masstemperature is raised to 55±2° C. while stirring. The clarity of thesolution is checked visually. If the solution is not clear, then 0.50 Xkg of methanol is charged into Reactor 2-A through Dosing Tank by usingresidual vacuum at 55±2° C. under stirring and vacuum is released usingnitrogen. This procedure can be repeated until the solution is clear.Once the solution is clear, the mass is transferred from Reactor 2-A toReactor B/C through Cartridge Filter by using vacuum at 55±2° C. Themass is slowly cooled to 30±5° C. and then chilled to 7.5±2.5° C. Themass is stirred at 7.5±2.5° C. for 3 hours ±5 minutes.

INTERMITTENT CLEANING: The Centrifuge is flushed with 5.00 kg ofmethanol.

PRODUCT ISOLATION: The mass obtained is filtered from Reactor B/Cthrough the Centrifuge at RPM of 500±50 under nitrogen atmosphere. TheCentrifuge RFM is raised to 950±50 and the material is spin dried. 0.79X kg of methanol is charged into the mixing vessel MV-0101 throughcharging line under nitrogen atmosphere. The methanol is chilled to7.5±2.5° C. The chilled methanol is unloaded from mixing vessel MV-0101into a HDPE container and Reactor B/C is flushed with chilled methanolunder nitrogen atmosphere. The wet cake is washed with chilled methanolobtained from Reactor B/C in the Centrifuge at RPM of 500±50 undernitrogen atmosphere. The Centrifuge RPM is raised to 950±50 and thematerial is spin dried. The centrifuge is stopped and after waiting for10±2 minutes, the spin dried material is unloaded under nitrogenatmosphere.

DRYING: The spin dried material is charged in to the dryer VTD-101/102and is dried at a temperature of 43±2° C. and under a vacuum of NLT 650mmHg for 10 hours ±5 minutes. The Loss on drying (% w/w) at 10^(th) houris checked. A sample should have a specification limit of NMT 1.0%. Oncethe drying is complete, drying is and the vacuum is released withnitrogen in the dryer. The dried material is unloaded and weighed.

YIELD: The expected yield is about 0.50 X to 0.75 X. The percentageyield [percentage yield=(Achieved Yieldx100)/Theoretical Yield] is aboutfrom 46.29 to about 69.44%.

Example 3 Stage III: Preparation of Purified 7,8,9,10-Tetrahydro-6,10-Methano-6H-Pyrazino[2,3-H][31]Benzazepine

The following is an illustration of the chemical reaction to produce7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine(Varenicline Free Base) starting from1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11.)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone(Quinoxaline). The synthetic procedure is discussed in details below.Throughout this synthetic procedure, X=27.00±3.00 kg of VareniclineTartrate Maltodextrin Premix (1:10) Stage-02(1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanoneor (Quinoxaline)) and Y=quantity of Semi Dried Material A.

PRE-CLEANING: Reactor B/C and Reactor 2-A are flushed each with 10 L ofpurified water. The flushed purified water is drained in lean effluentand the reactors are dried under vacuum. Reactor C and Sparkler filterSF-0104 are each flushed with 10.00 kg of methylene dichloride. ReactorC is dried under vacuum. The Nutsche filter SSNF-301/NF-0303 is flushedwith 10.00 kg of methanol. The Mixing Vessel MV-0101 is flushed with5.00 kg of methanol. The filter cloth is fixed and the sparkler filterSF-0104 is assembled. The Cartridge Filter is flushed with 2.00 kg ofmethylene dichloride. The Vacuum Tray Dryer is flushed with 10.00 kg oftertiary butyl methyl ether and the dryer is dried under vacuum. TheHolding Tank is flushed with 5.00 kg of methylene dichloride.

PREPARATION OF AQUEOUS SODIUM CARBONATE SOLUTION: 6.25 X L of purifiedwater and 0.69 X kg of sodium carbonate are charged into Reactor 2-A andthe mass is stirred until clear.

PREPARATION OF SODIUM CHLORIDE SOLUTION: 2.86 X L of purified water and1.00 X kg of sodium chloride are charged into Reactor B/C and the sodiumchloride solution is stirred for 10±5 minutes.

REACTION: 4.00 X kg of methanol is charged into Reactor B/C throughcharging line under nitrogen atmosphere. 1.00 X kg of VareniclineTartrate Maltodextrin Premix (1:10) Stage-02 (or(1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone)is charged into the reactor through Reactor B/C manhole/PTS/Powdercharging AOD the manhole at 30±3° C. Reactor B/C is flushed with 0.74 Xkg of methanol at 30±3° C. under nitrogen atmosphere. The mass isstirred at 30±3° C. for 15±5 minutes. The aqueous sodium carbonatesolution is slowly transferred from Reactor 2-A into Reactor B/C throughtransfer line at 30±3° C. and the reaction mass is stirred at 30±3° C.for 15±5 minutes. The temperature of reaction mass is raised to 67±3° C.

INTERMITTENT CLEANING: Reactor 2-A is flushed with 10.00 kg of methanol.

The mass is stirred at 67±3° C. for 3 hours ±5 minutes. To monitor thereaction, a sample is checked for varenicline tartrate Stage-02 (this is1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone orQuinoxaline) content by HPLC analysis. The content should be NMT 0.10 (%area). If varenicline tartrate Stage-02 by HPLC sample does not complythe limit, the reaction mass is maintained at a temperature of 67±3° C.and a sample is checked at an interval of every 2 hours until complies.The reaction mass is then cooled to 30±3° C.

FILTRATION: The reaction mass is filtered from Reactor B/C throughNutsche filter SSNF-301/NF-0303 under nitrogen atmosphere. Using vacuum,the material is suck dried under nitrogen atmosphere until the rate ofremoval of the mother liquor reduces to few drops per minute as observedvisually. Reactor B/C is flushed with 1.58 X kg of methanol. The wetcake is washed with the flushed methanol obtained from the previousoperation. Using vacuum, the material is suck dried under nitrogenatmosphere until the rate of removal of the filtrate reduces to fewdrops per minute as observed visually. The wet cake is uploaded from theNutsche filter.

INTERMITTENT CLEANING: Reactor B/C is flushed with 10.00 kg of methanol.

DISTILLATION: The filtrate is charged into Reactor B/C throughvacuum/charging nozzle under nitrogen atmosphere. A vacuum of NLT 650mmHg is applied to Reactor B/C. Next, 3.0 X-6.0 X kg of methanol isdistill out under vacuum NLT 650 mmHg and temperature of NMT 50° C. Thevacuum is released using nitrogen in Reactor B/C. The mass is cooled to30±3° C. and 5.00 X L of purified water is charged into Reactor B/C at30±3° C. 1.25 X kg of sodium chloride is charged into Reactor B/C at30±3° C. under nitrogen atmosphere. The mass is stirred at 30±3° C. for15±5 minutes.

EXTRACTION-I: 6.65 X kg of methylene dichloride is charged into ReactorB/C line under nitrogen atmosphere. The mass is stirred at 30±3° C. for20±5 minutes. Next, stirring is stopped and the mass is allowed tosettle for 20±5 minutes. The bottom organic layer (product layer) isseparated from Reactor B/C into the Holding Tank and the top aqueouslayer is retained in the reactor itself. The extraction is repeated 3times further (total of 4 extractions).

INTERMITTENT CLEANING: Reactor B/C is flushed with 10 L of purifiedwater and the flushed water is drained into strong effluent.

The organic layer from the Holding Tank is transferred to Reactor 2-Aunder nitrogen atmosphere. The sodium chloride solution from Reactor B/Cis transferred to Reactor 2-A under nitrogen atmosphere. The mass isstirred at 30±3° C. for 20±5 minutes and then allowed to settle for 20±5minutes. The bottom organic layer is separated from Reactor 2-A intoHolding Tank and the aqueous layer is collected into the separatecontainer.

INTERMITTENT CLEANING: Reactor 2-A is flushed with 10.00 kg of methanoland then with 10.00 kg of methylene dichloride.

PREPARATION OF HYFLO BED IN SPARKLER FILTER: 130.00 kg of methylenedichloride is charged in Reactor 2-A through the reactor charging lineunder nitrogen atmosphere. 5.00 kg of hyflo is charged into Reactor 2-Athrough the reactor manhole and stirring is started until the hyflo iscompletely dispersed in the methylene dichloride. The hyflo is filteredthrough sparkler filter SF-0104 and a hyflo bed is formed. This step isre-circulated until a clear filtrate is obtained and the methylenedichloride is then drained from Reactor 2-A in a clean HDPE container.The methylene dichloride is drained from the sparkler filter beforefiltration only.

INTERMITTENT CLEANING: Reactor 2-A and Reactor C are flushed each with10.00 kg of methylene dichloride.

The organic layer is transferred from the Holding Tank to Reactor 2-Athrough transfer line under nitrogen atmosphere. 0.10 X kg of activatedcarbon is charged into Reactor 2-A through the manhole at 30±3° C. andthe mass is stirred at 30±3° C. for 30±5 minutes. The reaction mass isthen filtered from Reactor 2-A through the Sparkler Filter SF-0104 andthe filtrate is transferred to Reactor C through Cartridge Filter undernitrogen atmosphere (before filtration, the methylene dichloride isdrained from Sparkler Filter). Next, 2.66 X kg of methylene dichlorideis charged into Reactor 2-A through charging line under nitrogenatmosphere. The methylene dichloride obtained from Reactor 2-A isfiltered through the Sparkler filter SF-0104 and the filtrate istransferred to Reactor C through Cartridge Filter under nitrogenatmosphere. A vacuum is applied to Reactor C.

DISTILLATION: Methylene dichloride is distilled out under vacuum andtemperature of NMT 40° C. 1.48 X kg of tertiary butyl methyl ether ischarged into Reactor C by using vacuum. Next, tertiary butyl methylether is distilled out under vacuum and temperature of NMT 40° C. Thevacuum is released using nitrogen. The mass is cooled to 30±3° C. Next,2.96 X kg of tertiary butyl methyl ether is charged into Reactor Cthrough charging line under nitrogen atmosphere at 30±3° C. The mass isstirred at 30±3° C. for 1 hour ±5 minutes. The mass is chilled to 7±3°C. and stirred for 2 hours ±5 minutes.

INTERMITTENT CLEANING: The Nutsche filter SSNF-301/NF-0303 is flushedwith 5.00 kg of tertiary butyl methyl ether.

PRODUCT ISOLATION: The reaction mass is filtered from Reactor C throughthe Nutsche filter SSNF-301/NF-0303 under nitrogen atmosphere. Usingvacuum, the material is suck dried under nitrogen atmosphere. The motherliquor is collected in a clean HDPE container. Reactor C is flushed withtertiary butyl methyl ether under nitrogen atmosphere and the flushedtertiary butyl methyl ether is transferred to mixing vessel MV-0101. Thewet cake in the Nutsche filter is washed with the flushed tertiary butylmethyl ether from Reactor C and suck dried under nitrogen atmosphere.The mother liquor is collected in the HDPE container. The suck driedmaterial is unloaded from the Nutsche filter under nitrogen atmosphere.The suck dried material is dried at a temperature of 43±2° C. and undera vacuum of NLT 650 mmHg for 2 hours ±5 minutes. A sample of the semidried material (Semi Dried Material A) is weighed and collected foranalysis.

PREPARATION OF AQUEOUS SODIUM CARBONATE SOLUTION: 10.00 Y L of purifiedwater and 1.00 Y kg of sodium carbonate are charged into Reactor 2-A andstirred.

PREPARATION OF L(+)TARTARIC ACID SOLUTION: 5.00 Y L of purified water ischarged into a clean HDPE container and 0.78 Y kg of L (+) Tartaric acidis charged into the same HDPE container. The mixture is stirred to getclear solution.

INTERMITTENT CLEANING : Reactor B/C is flushed first with 10.00 kg ofmethanol and then with 10.00 kg of methylene dichloride.

PURIFICATION: 6.65 Y Kg of methylene dichloride is charged into thereactor B/C through charging line under nitrogen atmosphere. Semi DriedMaterial A is charged into Reactor B/C under nitrogen atmosphere. Themass is stirred at 30±5° C. for 10±5 minutes. The L(+)Tartaric acidsolution is charged into Reactor B/C under nitrogen atmosphere. Thereaction mass is stirred at 30±5° C. for 15±5 minutes. Stirring isstopped and the mass is allowed to settle for 20±5 minutes. The bottomorganic layer is separated from Reactor B/C into a clean HDPE containerand the top aqueous layer is retained in the reactor itself

6.65 Y Kg of methylene dichloride is charged into Reactor B/C throughcharging line under nitrogen atmosphere. The mass is stirred at 30±5° C.for 20±5 minutes. Stirring is stopped and the mass is allowed to settlefor 20±5 minutes. The bottom organic layer is separated from Reactor B/Cinto a clean HDPE container and the top aqueous layer is retained in thereactor itself.

The aqueous sodium carbonate solution is transferred into Reactor B/Cfrom the Reactor 2-A through transfer line under nitrogen atmosphere.The mass is stirred at 30±5° C. for 20±5 minutes.

EXTRACTION: 13.30 Y kg of methylene dichloride is charged into ReactorB/C through charging line under nitrogen atmosphere. The mass is stirredat 30±5° C. for 20±5 minutes. Stirring is stopped and the mass isallowed to settle for 20±5 minutes. The bottom organic layer isseparated from Reactor B/C into the Holding Tank and the top aqueouslayer is retained in the reactor itself. The extraction is repeatedthree times further. At the end, the aqueous layer is unloaded into theseparate container.

INTERMITTENT CLEANING: Reactor C is flushed with 10 L of purified waterand the flushed water is drained in strong effluent.

PREPARATION OF SODIUM CHLORIDE SOLUTION: 4.30 Y L of purified water and1.50 Y kg of sodium chloride are charged into Reactor C and the sodiumchloride solution is stirred for 10±5 minutes.

INTERMITTENT CLEANING: Reactor 2-A is flushed first with 10 L ofpurified water and then with 10.00 kg of methylene dichloride.

The organic layer is transferred from the Holding Tank to Reactor 2-Athrough transfer line under nitrogen atmosphere. The sodium chloridesolution is transferred from Reactor C into Reactor 2-A through transferline under nitrogen atmosphere. The mass is stirred at 30±5° C. for 20±5minutes. Stirring is stopped and the mass is allowed to settle for 20±5minutes. The bottom organic layer is separated from Reactor 2-A intoHolding Tank and the aqueous layer is collected into a separatecontainer.

INTERMITTENT CLEANING: Reactor C is flushed with 10.00 kg of methylenedichloride and the Cartridge Filter is flushed with 2.00 kg of methylenedichloride.

The organic layer is transferred from Holding Tank through CartridgeFilter into Reactor C through charging line under nitrogen atmosphereand vacuum is applied to Reactor C.

DISTILLATION: Methylene dichloride is distilled out under vacuum andtemperature of NMT 40° C. 1.48 Y kg of tertiary butyl methyl ether ischarged into Reactor C by vacuum/charging line under nitrogenatmosphere. Next, tertiary butyl methyl ether is distilled under vacuumand temperature of NMT 40° C. The vacuum is released using nitrogen andthe mass is cooled to 30±3° C.

2.96 Y kg of tertiary butyl methyl ether is flushed into Reactor C undernitrogen atmosphere at 30±3° C. The mass is stirred at 30±3° C. for 1hour ±5 minutes and then chilled to 7±3° C. Next, the mass is stirred at7±3° C. for 2 hours ±5 minutes.

INTERMITTENT CLEANING: The Nutsche filter SSNF-301/NF-0303 is flushedwith 5.00 kg of tertiary butyl methyl ether.

PRODUCT ISOLATION: The reaction mass is filtered from Reactor C throughthe Nutsche filter SSNF-301/NF-0303 under nitrogen atmosphere. Usingvacuum, the material is suck dried under nitrogen atmosphere. Reactor Cis flushed with 0.74 Y kg of tertiary butyl methyl ether under nitrogenatmosphere and the flushed tertiary butyl methyl ether is transferred tomixing vessel MV-0101. The flushed tertiary butyl methyl ether ischilled to 7±3° C. and unloaded in HDPE container. Reactor C is flushedwith chilled tertiary butyl methyl ether under nitrogen atmosphere.Vacuum in Nutsche filter SSNF-301/NF-0303 is released using nitrogen.The wet cake in the Nutsche filter is washed with the flushed tertiarybutyl methyl ether from Reactor C and suck dried under nitrogenatmosphere.

0.74 Y kg of tertiary butyl methyl ether is charged into the mixingvessel MV-0101 under nitrogen atmosphere. The flushed tertiary butylmethyl ether is chilled to 7±3° C. and unloaded in HDPE container.Reactor C is flushed with chilled tertiary butyl methyl ether undernitrogen atmosphere. Vacuum in Nutsche filter SSNF-301/NF-0303 isreleased using nitrogen. The wet cake in the Nutsche filter is washedwith the flushed tertiary butyl methyl ether from Reactor C and suckdried under nitrogen atmosphere. Vacuum in Nutsche filterSSNF-301/NF-0303 is released using nitrogen and the suck dried materialis unloaded under nitrogen atmosphere.

INTERMITTENT CLEANING: The Vacuum Tray Dryer is flushed with 10.00 kg oftertiary butyl methyl ether .The dryer is dried under vacuum.

DRYING: The suck died material is dried at a temperature of 43±2° C. andunder a vacuum of NLT 650 mmHg for 14 hours±5 minutes. Sample is checkedfor Loss on Drying (Specification Limit : NMT 2.0 (% w/w)). If complies,the vacuum in the dryer is released with nitrogen. The dried material isallowed to rest for 10±2 minutes and then is unloaded in an innertranslucent and outer black polyethylene bags, weighed, a sample istaken for testing and the bags are closed. Material is stored at atemperature of 2° C. to 8° C.

YIELD: The expected yield is about 0.20 X to 0.60 X. The percentageyield [Percentage Yield=(Achieved Yieldx100)/Theoretical Yield] is fromabout 28.98 to about 86.95%.

Example 4 STAGE IV: Preparation of Varenicline Tartrate MaltodextrinPremix (1:10)

The following is an illustration of the chemical reaction to produce7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine,(2R,3R)-2,3-dihydroxybutanedioate.MaltodextrinPremix (Varenicline Tartrate Maltodextrin Premix (1:10)) starting from7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3 ]benzazepine(Varenicline Free Base). The synthetic procedure is discussed in detailsbelow. Throughout this synthetic procedure, X=1.00±0.20 kg ofVarenicline Tartrate Maltodextrin Premix (1:10) stage-03 (or7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3 ]benzazepine(Varenicline Free Base)) after LOD correction and Y=calculated quantityof L(+) Tartaric acid. *Dry weight of Stage-3 is calculated using thefollowing formula:

${{Actual}\mspace{14mu}{weight}\mspace{14mu}(X)} = {{{Dry}\mspace{14mu}{weight}\mspace{14mu}{of}\mspace{14mu}{Stage}\text{-}3} - ( {\frac{{LOD}\mspace{14mu}{of}\mspace{14mu}{Stage}\text{-}3}{100} \times {Dry}\mspace{14mu}{weight}\mspace{14mu}{of}\mspace{14mu}{Stage}\text{-}3} )}$

**Weight of L(+)Tartaric acid is calculated using the following formula:

${{Actual}\mspace{14mu}{weight}\mspace{14mu}(Y)} = ( \frac{{Stage}\text{-}3(X) \times 70.3}{{Assay}\mspace{14mu}{of}\mspace{14mu}{L( + )}\mspace{14mu}{Tartaric}\mspace{14mu}{acid}} )$

***Weight of Maltodextrin is calculated using the following formula:

Actual  weight  (Z) = 17.12 × Stage-3(X) + (Water  content  of  Maltodextrin × 0.1712 × Weight  of  Stage-3(X))

PRE-CLEANING: The mixing vessel MV-05-SD-1201 and the mixing vesselMV-1-5D-1201 are flushed each with 5.00 kg of methanol The feedpreparation vessel FPV-1-SD-1201 is flushed with 5.00 kg of purifiedwater and the flushed water is drained into the lean effluent. Thecartridge filter CGF-1205/ 1206 is flushed with 2.00 kg of methanol(Cartridge: 0.20 micron). Spray Dryer SD-1201 and vacuum tray dryerVTD-1201 are each flushed with 10.00 kg of methanol and dried. SifterSFT-1201 and its mesh are flushed with 5.00 kg of methanol. The sifteris wiped thoroughly with lint free cloth and dried using nitrogen. 20 #sifter mesh is fixed in the sifter SFT-1201.

15.80 X kg of methanol is charged into mixing vessel MV-05-SD-1201. 1.00X kg of Varenicline Tartrate Maltodextrin Premix (1:10) stage-03 (or7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine(Varenicline Free Base)) is charged into Mixing vessel MV-05-SD-1201.The mass is stirred until clear solution is obtained and the solution istransferred to feed preparation vessel FPV-1-SD-1201.

PREPARATION OF L(+)TARTARIC ACID SOLUTION: 10.00 X kg of purified waterand 1.00 Y kg of L (+) Tartaric acid are charged into the mixing vesselMV-05-SD-1201. The mass is stirred until clear solution is obtained. Thesolution is transferred to feed preparation vessel FPV-1-SD-1201.

PREPARATION OF MALTODEXTRIN SOLUTION: 60.07 X kg of purified water and17.12 X kg of maltodextrin are charged into a mixing vesselMV-05-SD-1201. The mass is stirred until clear solution is obtained. Thesolution is transferred to feed preparation vessel FPV-1-SD-1201. Themass is stirred at 30±3° C. for 30±5 minutes in feed preparation vesselFPV-1-SD-1201. The mass is transferred from the feed preparation VesselFPV-1-SD-1201 to mixing vessel MV-1-SD-1201 through cartridge filterCGF-1205/1206 under nitrogen atmosphere and a clear solution isobtained.

The mixing vessel MV-05-SD-1201 is flushed with 20.00 X kg of purifiedwater. The flushed purified water is transferred to feed preparationvessel FPV-1-SD-1201. The flushed water is filtered from the feedpreparation Vessel FPV-1-SD-1201 to mixing vessel MV-1-SD-1201 throughcartridge filter CGF-1205/1206 under nitrogen atmosphere to obtain clearsolution.

SPRAY DRYING: Spray dryer SD-1201 needs to be visually clean and dry.Nitrogen gas pressure is used for atomization. Plain solvent mixture(Mixture A) with 3.60 kg of methanol and 16.40 kg of purified water isprepared in HDPE container. The spray dryer is switched on, the requiredparameters in spray dryer are set as shown in Table 10, and the spraydryer is run with plain solvent mixture (Mixture A) to achieve steadystate. The solution is fed to the spray dryer SD-1201 from the mixingvessel MV-1-SD-1201.

TABLE 10 Required Parameters in Spray Dryer Inlet Temperature  130 ± 15°C. ID Blower flow rate  750 ± 150 NM³/hr FD Blower flow rate  400 ± 100NM³/hr Atomization Pressure  3.6 ± 0.6 kg/cm² Feed flow rate   60 ± 30ml/min

The spraying chamber of Spray dryer is intermittently cleaned withpurified water for every 3 hours ±5 minutes and dried using nitrogen.The spray dryer is run with plain solvent mixture to achieve steadystate. The feed solution is fed for NMT 3 hours. The material from thespray dryer is unloaded under nitrogen atmosphere. The spray driedmaterial is charged into the dryer VTD-1201. Initial Residual SolventAnalysis is conducted using GC. The results are provided in Table 11below.

TABLE 11 RESIDUAL OF SOLVENT BY GC Test Parameters Specification Limit[observed results] a. Methanol NMT 3000 ppm [700-2300 ppm] b. MTBE NMT5000 ppm [Not detected] c. Methylene dichloride NMT 600 ppm [Notdetected]

DRYING: The material is dried at a temperature of 35±5° C. and under avacuum of NLT 650 mmHg for 12 hours ±5 minutes. The Loss on Drying ischecked (specification limit: NMT 3.5% w/w). Once the sample complieswith this limit, the drying is stopped and the vacuum is released withnitrogen. After 10±2 minutes, the dried material is unloaded undernitrogen atmosphere and weighed.

SIFTING: The bag containing the dried material is tied in the dischargechute under of the sifter SFT-1201 to collect the sifted material undernitrogen atmosphere. The sifter SFT-1201 is turned on and the materialis charged into the sifter using a clean scoop under nitrogenatmosphere. The sifter is run until the completion of the sifting andthe sieved material is collected into a bag fixed in the discharge chuteunder nitrogen atmosphere and weighed. The material is moved to coldstorage area.

YIELD: The expected yield is about 8.00 X to 18.0 X. The percentageyield [Percentage Yield =(Achieved Yieldx100)/Theoretical Yield] is fromabout 42.78 to about 96.25%.

Example 5 Characterization of Varenicline Tartrate Maltodextrin Premix(1:10)

The Scanning Electron Microscopy (SEM) was used for imaging ofcrystalline API-PAT (crystalline varenicline tartrate salt) (FIG. 2),maltodextrin (Glucidex 12D) (FIG. 3), API Premix (varenicline tartrate:Maltodextrin −1:10) PAT (FIG. 4) and API+Maltodextrin (Physical Mix)(1:10) (FIG. 5).

The spray drying process renders a near spherical morphology of thepremix of the present disclosure, as observed from the SEM images. Suchmorphology is not observed in the physical mixture between vareniclinetartrate and maltodextrin, in the same weight ratio as that used in thepremix (i.e. 1:10). This result shows that the spray drying process ofthe present disclosure produces nearly spherical shaped particles, wherevarenicline tartrate is uniformly dispersed in maltodextrin matrix.

The near to spherical morphology of the spray dried premix, offersminimal surface area for the premix, as for a given volume, a sphericalshape has the lowest surface area. This low surface area of the premixparticles is likely to be a key factor, contributing to lower extent ofinteraction (contact) between the premix particles and the otherexcipients used in the formulation, thus reducing the chances ofgeneration of any impurities that is likely to be formed because of suchinteraction (contact).

The reduction of the surface:volume ratio by creating sphericalagglomerations of the varenicline/maltodextrin mixture reduces theamount of contact between the active and other excipients, therebydiminishing the likelihood of impurity generation.

Such morphology is not observed in the physical mixture betweenVarenicline Tartrate & Maltodextrin, in the same weight ratio as thatused in the premix (i.e. 1:10). This shows that the spray drying processof the current disclosure produces nearly spherical shaped particles,where Varenicline tartrate is uniformly dispersed in maltodextrinmatrix.

The near to spherical morphology of the spray dried premix, offersminimal surface area for the premix, as for a given volume, a sphericalshape has the lowest surface area.

This low surface area of the premix particles is likely to be a keyfactor, contributing to lower extent of interaction (contact) betweenthe premix particles and the other excipients used in the formulation,thus reducing the chances of generation of any impurities that is likelyto be formed because of such interaction (contact).

Example 6 X-Ray Diffraction Studies

The X-ray diffractorgram of varenicline tartrate shows presence ofsignature peaks for Crystalline form B (FIG. 6A and FIG. B). On theother hand, the spray drying process results in varenicline -maltodextrin premix which exist in the amorphous form, as observed bythe X-ray diffraction studies (FIG. 7).

The dilution of varenicline tartrate in the spray dried premix form islikely to be responsible for lowering the contact of the drug substancewith the other excipients in the formulation. This effect may help incontrolling the levels of impurities in the drug product of the currentdisclosure, which are formed by the interaction of the drug substancewith the excipients, when they come in close contact.

The spray drying process results in Varenicline - maltodextrin premixwhich exist in the amorphous form, as observed by the X-ray diffractionstudies.

The dilution of Varenicline tartrate in the spray dried premix form islikely to be responsible for lowering the contact of the drug substancewith the other excipients in the formulation.

This may help to control the levels of impurities in the drug productmanufactured by Applicant, which are formed by the interaction of thedrug substance with the excipients, when they come in close contact.

Example 7 Testing for Impurities

LC-ESI-HRMS Method for the Determination of Varenicline Nitroso-DrugSubstance Related Impurity, U.S. FDA, Aug. 6, 2021,https://www.fda.gov/media/151470/download (accessed Feb. 27, 2022) canbe used to test for impurities.

Other analytical methods for the entire process can be used to test forimpurities. The methods are validated as per ICH guideline.

For example, HPLC RS methods are used for quantifying the impurities.The nitrosamines, monomethyl and dimethyl tartaric acid esters arequantified by LCMS methods.

EXAMPLE 8 Analytical Methods for Analyzing Varenicline Base (STAGE 3)and Varenicline Tartrate Maltodextrin Premix Api

Two Related Substance methods by HPLC were developed for analyzingVarenicline base (Stage 3) for quantifying all impurities having asimilar chromophore of Varenicline. The same two HPLC methods wereadopted for analyzing the Varenicline Tartrate Maltodextrin Premix APIfor quantifying the respected impurities. A third additional RS methodby HPLC was developed for analyzing two additional impurities viz.N-methyl Varenicline and Varenicline-N-Gluoside which could form due toreaction of degradation products of Maltodextrin with Varenicline.Moreover, two LCMS methods were developed for analyzing monomethyl anddimethyl esters of tartaric acid as impurities in Varenicline TartrateMaltodextrin premix API. Furthermore, two LCMS methods were developedfor quantifying the Nitrosamine impurities in Varenicline TartrateMaltodextrin Premix API. The detailed methods and LOD and LOQ values arediscussed below. Lists of the Related Substances Method-I and RelatedSubstances Method-II are provided in Tables 12 and 13, respectively.

TABLE 12 Related Substances Method-I Related substances by HPLC(Method-I) (% w/w) Chemical Name of the Impurities Limits (% w/w)Impurity D (2,3,4,5-tetrahydro-1H-1,5-methano-3- Not more than 0.0438benzazepine-6,8-diamine) Impurity F (7,8-Diamino-2,3,4,5-tetrahydro-1H-Not more than 0.0438 1,5-methano-3-benzazepine) Impurity C(2,3,4,5-tetrahydro-1H-1,5-methano-3- Not more than 0.0438benzazepin-7-amine) Methyl Varenicline2-methyl-7,8,9,10-tetrahydro-6H-6,10- Not more than 0.15methanoazepino[4,5-g]quinoxaline Varenicline Stage-011-(4,5-diamino-10-aza-tricyclo Not more than 0.0438[6.3.1.02-7]dodeca-2(7),3,5-trien- 10-yl)-2,2,2-trifluoro-ethanone(Diamino protected) Varenicline Stage-02 1-(5,8,14-Triazatetracyclo Notmore than 0.15 [10.3.1.0^(2, 11).0^(4, 9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2- trifluro-ethanone (Quinoxaline)Varenicline KSM 1-(4,5-dinitro-10-aza-tricyclo[6.3.1.0 ^(2, 7)] Not morethan 0.0438 dodeca-2(7),3,5-trien-10-yl)-2,2,2- trifluoro-ethanone(Dinitro protected)

TABLE 13 Related Substances Method-II Related substances by HPLC(Method- II) (% w/w ) Chemical Name of the Impurities Limits (% w/w)Mononitro deprotected 7-nitro-2,3,4,5-tetrahydro-1H-1,5- Not more than0.0438 methano-3-benzazepine Metadinitro 3,5-Dinitro-10-aza-tricyclo Notmore than 0.0438 deprotected [6.3.1.0^(2, 7)]dodeca-2,4,6-triene or2,3,4,5-tetrahydro-6,8-dinitro-1,5-methano- 1H-3-benzazepine or6,8-dinitro-2,3,4,5-tetrahydro-1H-1,5- methano-3-benzazepine Metadiamino3-(trifluoroacetyl)-2,3,4,5-tetrahydro-1H- Not more than 0.0438protected 1,5-methano-3-benzazepine-6,8-diamine Varenicline Impurity-(7,8-Dinitro-2,3,4,5-tetrahydro-1H-1,5- Not more than 0.0438 Gmethano-3-benzazepine) Monoamino protected3-(trifluoroacetyl)-2,3,4,5-tetrahydro-1H- Not more than 0.04381,5-methano-3-benzazepin-7-amine Mononitro protected7-nitro-3-(trifluoroacetyl)-2,3,4,5- Not more than 0.0438tetrahydro-1H-1,5-methano-3-benzazepine Metadinitro protected6,8-dinitro-3-(trifluoroacetyl)-2,3,4,5- Not more than 0.0438tetrahydro-1H-1,5-methano-3-benzazepine Individual unspecified Not morethan 0.10 impurity Total impurities Not more than 1.0

Calculation for the limit fixed(Genotoxic)=PDE(ps/day)/MDD(mg/day)=1.5/3.42=0.438 ppm or 0.0438% w/w .

MDD=3.42 mg of Varenicline Tartrate per day

A list of process impurities controlled in varenicline tartratemaltodextrin premix is provided in Table 14.

TABLE 14 List of Process Impurities Controlled in Varenicline TartrateMaltodextrin Premix Limit S. No Impurities (% w/w) Method 1 N-FormylVarenicline 0.15 Adopted RS Method-II 2 Diamide Impurity 0.15 3 N-MethylVarenicline 0.15 Related Substances 4 Varenicline-N Glucoside 0.15Method-III 5 Tartaric acid Monomethyl ester 0.15 LCMS-ESI 6 Tartaricacid Dimethyl ester 0.15 LCMS-APCI Nitrosoamine 7 Nitroso VareniclineImpurity 5.26 ppm LCMS Method-I 8 Dinitro Nitrosamine Impurity 5.26 ppm9 Diamino Nitrosamine Impurity 5.26 ppm LCMS Method-II Note: Processimpurity N-formyl Varenicline and Diamide Impurity has been controlledwith 0.15% w/w Varenicline Tartrate Maltodextrin premix (1:10) by usingMethod-II

A. Related Substances Method-I for Analyzing Varenicline Base (Stage 3)(RS Method-I)

Related substance By HPLC (Method-I): Waters HPLC system having Alliance2695 model pump and 2487 or equivalent (UV) detector with Empowerchromatographic software or its equivalent.

Reagents: A list of the reagents used in this method is provided inTable 15.

TABLE 15 List of Regents used in Related Substances Method-I S. No. Nameof the solvents Grade Make 1 Diammonium hydrogen AR Merck or itsequivalent phosphate 2 Ortho Phosphoric acid AR Rankem or its equivalent(85 %) 3 Methanol HPLC JT Baker or its equivalent 4 Acetonitrile HPLC JTBaker or its equivalent 5 Water Milli-Q —

Chromatographic Parameters:

Column : X Terra C18 (250×4.6) mm, 5.0 μ

Detector wavelength : UV at 210nm

Flow rate :1.0 mL/min

Injection volume : 30.0 μL

Run time : 70 minutes

Oven temperature : 30° C.

Sample cooler temperature : 7° C.

Elution : Gradient

Diluent: 0.10% v/v Ortho Phosphoric acid: Methanol (95:05) (v/v)

Buffer preparation: Use 0.02 M of di-ammonium hydrogen phosphatesolution, pH adjust to 7.00 (+0.05) using dilute orthophosphoric acid.

Preparation of organic modifier: Premix acetonitrile and Methanol in theratio of (50:50) (v/v).

Mobile Phase -A: Prepare a premixed and degassed mixture of Buffer:Organic modifier (95:5) (v/v)

Mobile Phase -B: Prepare a premixed and degassed mixture of Buffer:Organic modifier (10:90) (v/v)

Gradient Program

Time (min): 0, 5, 15, 20, 35, 45, 55, 60, 70

Mobile phase B (%): 0, 0, 25, 25, 40, 60, 75, 0, 0

-   -   Standard Solution: 0.5 μg/ml of Varenicline Tartrate in Diluent.        (0.3 μg/ml of Varenicline)    -   Sample Preparation: 500 μg/ml (Duplicate Preparation)    -   System Suitability solution: 0.38 μg/ml of both D and F Impurity

System suitability Acceptance Criteria:

-   -   a) USP Resolution between D and F is not less than 1.5    -   b) % RSD of the area of the Varenicline from Six Replicate        injection is Not more than 5.0%.

Table 16 provides the retention time (RT) and relative retention time(RRT) of the impurities.

TABLE 16 RT and RRT of the Impurities About RT Approximate (% w/w) S. NoName (mins) RRT RRF LOD LOQ 1 Impurity-D 4.4 0.32 0.79 0.004 0.013 2Impurity-F 5.2 0.37 1.27 0.004 0.012 3 Impurity-C 7.1 0.51 0.68 0.0040.013 4 Varenicline 13.8  1.00 — 0.002 0.006 5 Methyl Varenicline 16.0 1.16 2.13 0.002 0.005 6 Varenicline Stage-01 25.3  1.83 1.38 0.003 0.0087 Varenicline Stage-02 33.0  2.38 1.52 0.004 0.013 8 Varenicline KSM47.6  3.45 0.67 0.002 0.007 Known Impurity (% w/w) : (A_(t)/A_(s)) × (Cs/C_(t)) × 100/RRF Where, A_(s) = Average Area Response of StandardSolution A_(t) = Area Response of Sample Solution. Cs = StandardConcentration in μg/ml C_(t) = Sample Concentration in μg/ml RRF =Relative response of the Impurity.

B. Related Substances Method-II for Analyzing Varenicline Base (Stage 3)(RS Method-II)

Waters HPLC system having Alliance 2695 model pump and 2487 orequivalent (UV) detector with Empower chromatographic software or itsequivalent was employed in the analysis.

Reagents: A list of the reagents used in this method is provided inTable 17.

TABLE 17 List of Regents used in Related Substances Method-II S. No.Name of the solvents Grade Make 1 Ammonium dihydrogen AR Merck or itsequivalent phosphate 2 Ortho Phosphoric acid AR Rankem or its equivalent(85 %) 3 Methanol HPLC JT Baker or its equivalent 4 Acetonitrile HPLC JTBaker or its equivalent 5 Water Milli-Q —

Chromatographic Parameters:

-   Column: Purospher star RP-18 encapped (250×4.6) mm, 5.0 μ-   Detector wavelength: UV at 210 nm-   Flow rate: 0.8 mL/min-   Injection volume: 25.0 μL-   Run time: 52 minutes-   Column oven temperature: 45° C.-   Sample Cooler temperature: 10° C.-   Diluent: 0.1% Ortho phosphoric acid v/v : Methanol (85:15) (v/v)-   Elution: Gradient

Diluent: 0.10% v/v Ortho Phosphoric acid: Methanol (95:05) (v/v)

Mobile phase-A: Weigh and transfer about 3.45 g of Ammonium dihydrogenorthophosphate in 1000 mL water and add 2.0 ml of orthophosphoric acid85%, Filtered through 0.45 μm or fine porosity membrane and degass.

Mobile phase-B: Mix Acetonitrile, methanol and water in the ratio of 550: 500:50.

Gradient Program

Time (min): 0, 35, 40, 42, 52

Mobile phase B (%): 10, 70, 70, 10, 10

-   -   Standard Solution: 0.5 μg/ml of Varenicline Tartrate in Diluent        .(0.3 μg/ml of Varenicline)    -   Sample Preparation: 500 μg/ml (Duplicate Preparation)    -   System Suitability solution: 0.38 μg/ml of both Impurity G and        monoamino protected.

System suitability Acceptance Criteria:

-   -   a) USP Resolution between G and monoamino protected is not less        than 1.5    -   b) % RSD of the area of the Varenicline from Six Replicate        injection is not more than 5.0%.

Table 18 provides the RT and RRT of the impurities.

TABLE 18 RT and RRT of the Impurities About RT Approximate (% w/w) S. NoName (mins) RRT RRF LOD LOQ  1 Impurity-D# 3.1 0.31 Method-I Impurities 2 Impurity-C# 3.4 0.34 *Impurity-C, impurity-F  3 Impurity-F# 3.7 0.37and tartaric acid are merged in spiked sample preparation  4 Tartaricacid 3.5  0.37* Tartaric acid content method  5 N-Methyl Varenicline# 9.26 0.94 Method-III Impurities  6 VareniclineN-Glucoside#  9.29  7Varenicline 10.1  1.00 1.00 0.002 0.005  8 Metadiamino protected 11.9 1.17 1.56 0.003 0.009  9 Methyl Varenicline# 12.5  1.24 Method-IImpurity 10 Mononitro deprotected 12.9  1.27 0.70 0.002 0.005 11Metadinitro deprotected 14.1  1.39 0.45 0.002 0.008 12 VareniclineStage-01# 15.4  1.52 Method-I Impurity 13 Varenicline impurity-G 15.9 1.56 0.63 0.004 0.014 14 Monoamino protected 17.0  1.68 0.71 0.003 0.01015 N-Formyl Varenicline 17.75 1.82 1.64 0.003 0.008 16 VareniclineStage-02# 28.1  2.78 Method-I Impurities 17 Diamide impurity 29.42 3.011.44 0.002 0.007 18 Varenicline KSM# 35.2  3.48 Method-I Impurities 19Mononitro protected 35.8  3.53 0.70 0.002 0.007 20 Metadinitro protected37.0  3.65 0.66 0.003 0.009 # Note: In sample chromatograms, disregardthe impurities of RS Method I and RS Method III in RS Method II. KnownImpurity (% w/w) : (A_(t)/A_(s)) × (Cs/C_(t)) × 100/RRF

Where, A_(s)=Average Area Response of Standard Solution

-   -   A_(t) =Area Response of Sample Solution.    -   C_(s)=Standard Concentration in μg/ml    -   C_(t)=Sample Concentration in μg/ml    -   RRF=Relative response of the Impurity.        Unspecified Impurity (% w/w): (A_(t)/A_(s))×(Cs/C_(t))×100×M₁/M₂

Where, A_(s)=Average Area Response of Standard Solution

-   -   A_(t)=Area Response of Sample Solution.    -   C_(s)=Standard Concentration in μg/ml    -   C_(t)=Sample Concentration in μg/ml    -   M₁=Molecular weight of Varenicline free base (211.26 g/mol)    -   M₂=Molecular weight of Varenicline Tartrate (361.35 g/mol)

C. Related Substance Method III For Analyzing Varenicline TartrateMaltodextrin Premix (1:10) (Stage 4) (RS Method-III)

This method is used as a control of N-methyl varenicline andVarenicline-N-glucoside impurity in varenicline tartrate maltodextrinpremix (1:10).

Instrumentation: HPLC equipped with UV detector (Waters—Alliance withEmpower software or equivalent)

Chromatographic Parameters:

-   Column: Waters X-Bridge RP Shield C18 or equivalent-   (Length: 250 mm, Diameter:4.6 mm, Particle size: 3.5 μ)-   Detector wavelength: UV at 210 nm-   Flow rate: 0.6 mL/min-   Injection volume: 25.0-   Run time: 45 minutes-   Column oven temperature: 45° C.-   Sample Cooler temperature: 10° C.-   Needle wash: Methanol: water (50:50)-   Elution: Gradient

Gradient Program

Time (min) : 0, 20, 23, 33, 35, 45

Mobile phase B (%) : 10, 35, 90, 90, 10, 10

Buffer: Weigh and dissolve about 2.64 g of di-ammonium hydrogenphosphate in 1000 mL water, adjust the pH to 7.00 (±0.05) using diluteorthophosphoric acid.

Preparation of organic modifier: Premix acetonitrile and Methanol in theratio of (50:50) (v/v).

Mobile Phase-A: Prepare a premixed and degassed mixture of Buffer:Organic modifier (95:5)(v/v)

Mobile phase-B: Mix Acetonitrile, methanol and water in the ratio of550: 500:50

Diluent: 0.1% OPA: Methanol (85:15) v/v

-   -   Standard Solution :Mixture 0.15 μg/ml of both N-Methyl        Varenicline and Varenicline-N-Glucoside Impurity    -   Sample Preparation : 550 mg of premix in 50 ml (1000 μg of        Varenicline Tartrate/ml (Duplicate Preparation)

System Suitability solution/RT Identification Solution: Vareniclinetartrate (1:10) Premix sample solution of 1000 μg/ml Vareniclinetartrate containing 0.15 μg/ml of each of Methyl Varenicline,Varenicline-N-Glucoside and meta-diamino protected impurity.

System Suitability Acceptance Criteria:

-   a) USP Resolution between Varenicline N-Glucoside and meta-diamino    protected is not less than 1.0-   b) % RSD of the area of the Varenicline from Six Replicate injection    is Not more than 5.0%.

Calculation:

-   Known Impurity (%w/w) : (A_(t)/A_(s))×(Cs/C_(t))×100 /9.09×100

Where, As =Average Area Response of Standard Solution

-   -   A_(t) =Area Response of Sample Solution.    -   C_(s)=Standard Concentration in μg/ml    -   C_(t)=Sample Concentration in μg/ml

D. RS Method-I, RS Method-II, and RS Method-III for Analyzing theVarenicline Tartrate Maltodextrin Premix API

The same three HPLC methods (Related Substances Method-I; RelatedSubstances Method-II; and Related Substances Method-III) were adoptedfor analyzing the Varenicline Tartrate Maltodextrin Premix API forquantifying the respected impurities. The results are provided in Tables19-21 and FIGS. 8A-10C. The specificity study chromatogram of theimpurities viz. N-methyl Varenicline, Varenicline N-Glucoside in RSmethod 1 are provided in FIG. 8E.

TABLE 19 RS Method-I (Adopted Method-I of Varenicline Base (Stage-03))About RT Approximate (% w/w) S. No Name (mins) RRT RRF LOD LOQ  1Tartaric acid# 2.4 0.18 Tartaric acid content method  2 Impurity-D 4.40.32 0.79 0.004 0.013  3 Impurity-F 5.2 0.37 1.27 0.004 0.012  4Impurity-C 7.1 0.51 0.68 0.004 0.013  5 Varenicline 13.7  1.00 — 0.0020.006  6 Mononitro deprotected# 15.3  1.10 Method-2 Impurity  7 MethylVarenicline 16.0  1.16 2.13 0.002 0.005  8 N-Methyl Varenicline* 16.3 1.19 Method-3 Impurity  9 N-Formyl Varenicline# 17.8  1.38 Method-2Impurity 10 Metadiamino protected# *ND ND *The above impurities 11Metadinitro deprotected# 21.9  1.53 response very low was observed inmethod- 1HPLC condition. 12 Varenicline N-Glucoside# 21.5  1.59 Method-3Impurity 13 Varenicline impurity-G# 24.1  1.70 Method-2 Impurity 14Varenicline Stage-01 25.3  1.83 1.38 0.003 0.008 15 Varenicline Stage-0233.0  2.38 1.52 0.004 0.013 16 Monoamino protected# *ND ND Method-2Impurity 17 Diamide impurity# 29.5  2.71 18 Mononitro protected# 46.6 3.32 19 Varenicline KSM 47.6  3.45 0.67 0.002 0.007 20 Metadinitroprotected# 48.5  3.47 Method-2 Impurity # Note: In sample chromatograms,the impurities of RS Method II and III were disregarded in RS Method I.*The specificity of the impurities viz. N-methyl Varenicline,Varenicline N-Glucoside in RS Method-I were performed separately. Thespecificity study chromatograms of the these impurities are provided inFIG. 8E.

TABLE 20 RS Method-II (Adopted Method-II of Varenicline Base (Stage-03)About RT Approximate (% w/w) S. No Name (mins) RRT RRF LOD LOQ  1Impurity-D# 3.2 0.31 Method-I Impurities  2 Impurity-C# 3.4 0.34*Impurity-C, Impurity-F  3 Impurity-F# 3.7 0.37 and tartaric acid aremerged in spiked sample preparation  4 Tartaric acid 3.5  0.37* Tartaricacid content method  5 N-Methyl Varenicline# 9.3 0.94 Method-3Impurities  6 Varenicline N-Glucoside# 20.5   7 Varenicline 9.7 1.001.00 0.002 0.005  8 Metadiamino protected 11.3  1.17 1.56 0.003 0.009  9Methyl Varenicline# 12.2  1.24 Method-I Impurity 10 Mononitrodeprotected 12.5  1.27 0.70 0.002 0.005 11 Metadinitro deprotected 13.7 1.39 0.45 0.002 0.008 12 Varenicline Stage-01# 14.8  1.52 Method-IImpurity 13 Varenicline impurity-G 15.4  1.56 0.63 0.004 0.014 14Monoamino protected 16.2  1.68 0.71 0.003 0.010 15 N-Formyl Varenicline17.8  1.82 1.64 0.003 0.008 16 Varenicline Stage-02# 27.6  2.78 Method-IImpurities 17 Diamide impurity 29.5  3.01 1.44 0.002 0.007 18Varenicline KSM# 34.8  3.48 Method-I Impurities 19 Mononitro protected35.3  3.53 0.70 0.002 0.007 20 Metadinitro protected 36.6  3.65 0.660.003 0.009 # Note: In sample chromatograms, the impurities of RS MethodI and RS Method III were disregarded in RS Method II.

TABLE 21 RS Method-III (Adopted Method-III of Varenicline Base(Stage-03)) About RT Approximate (% w/w) S. No Name (mins) RRT LOD LOQ 1Tartaric acid# 4.1 0.43 Tartaric acid content Method 2 Impurity-D# 5.60.53 Method-1 Impurities 3 Impurity-F# 5.6 4 Impurity-C# 6.7 0.69 5Varenicline Tartrate API 10.2 1.00 — 6 Methyl Varenicline # 12.8 1.25Method-1 Impurities 7 Mononitro deprotected # 14.9 1.46 Method-2Impurities 8 N-Methyl Varenicline 16.7 1.64 0.003 0.008 9 N-FormylVarenicline # 17.4 1.70 Method-2 Impurity 10 Varenicline N-Glucoside20.5 2.02 0.003 0.008 11 Meta diamino protected# 21.0 2.06 Method-2Impurity 12 Varenicline Stage-01# 25.2 2.47 Method-1 Impurity 13 Metadinitro 25.2 Method-2 Impurities deprotected# 14 Varenicline impurity-G#26.1 2.55 15 Varenicline Stage-02# 27.8 2.71 Method-1 Impurity 16Monoamino protected# 28.1 2.75 Method-2 Impurities 17 Diamide impurity#28.1 18 Varenicline KSM# 29.0 2.84 Method-1 Impurity 19 Mononitroprotected# 29.1 2.85 Method-2 Impurities 20 Meta dinitro protected# 29.22.85

E. Content of Tartaric Acid Monomethyl Ester by Lcms:

Instrumentation: UPLC equipped with MS detector (Waters—Acquity withMass lynx software and Xevo TQ Mass Detector)

Chromatographic Conditions:

Column Acquity UPLC CSH Flouro-phenyl (length: 150 mm, Diameter: 2.1 mm,Particle size: 1.7 μ) Flow rate 0.3 mL/min Week wash solventAcetonitrile:water (50:50) Name(% v/v) Strong wash solventAcetonitrile:water (90:10) Name(% v/v) Injection Volume 5 μl Column oventemperature 30° C. Sample cooler 10° C. Elution Gradient Run time 17minutes

Mass Parameters:

Start time and end time 0 to 17 minutes Ionization Mode ES Negative DataType SIR data Function Type SIR of one channel Scan time (Sec) 1.00 Dataformat Continuum Span (Da) 0.10

SIR

Mass Channel (Da) Dwell(s) Cone (v) Compound 1 163.03 0.025 18 Tartaricacid Monomethyl ester

Tune Method

Polarity ES Negative Capillary voltage 3 Kilo volt Cone-Voltage 18 voltSource temperature 150° C. Desolvation temperature 400° C. DesolvationGas Flow 800 (L/Hr) Cone Gas Flow 50 (L/Hr)

Mass divert Program:

Event Retention time (RT) mins Flow state 1 0.00 Waste 2 (RT_(s) − 1)Waste 3 (RT_(s) − 1) + 0.01 LC 4 (RT_(s) + 1.5) LC 5 (RT_(s) + 1.51)Waste

Gradient Program:

Time (mins) Mobile Phase-A (%) Mobile Phase-B (%) Initial 90 10 4.00 9010 8.00 20 80 11.00 20 80 12.00 90 10 17.00 90 10

Mobile Phase A: 0.1% Formic acid in water. (1 ml in 1000 ml water)

Mobile Phase B: Acetonitrile

Diluent: 0.1% Formic acid in water: Acetonitrile (90:10)% v/v

Standard solution: 0.002% concentration in diluent

Sample Preparation: 15mg/ml in diluent

Concentration (% w/w) LOD LOQ Tartaric acid Monomethyl ester 0.005 0.015

Calculation:

Content of Tartaric acid Monomethyl ester (% w/w)

$\frac{A_{2}}{A_{1}} \times \frac{W_{1}}{W\; 2} \times \frac{100}{Y} \times 106$

Where:

-   A₂=Peak area of Tartaric acid Monomethyl ester impurity in sample-   A₁=Average Peak area Tartaric acid Monomethyl ester impurity in    standard-   W₁=standard concentration-   W₂=Sample concentration-   P=Purity of Tartaric acid Monomethyl ester impurity standard-   Y=9.09 (i.e. Theoretical Label claim of Varenicline tartrate in    Varenicline Tartrate Maltodextrin Premix (1:10) in %)

F. Content of Tartaric Acid Dimethyl Ester by LCMS:

Instrumentation: UPLC equipped with MS detector (Waters—Acquity withMass lynx software and Xevo TQ Mass Detector)

Chromatographic Conditions:

Column Acquity UPLC BEH C18 (length: 150 mm, Diameter: 2.1 mm, Particlesize: 1.7μ) Flow rate 0.3 mL/min Week wash solvent Name Acetonitrile:water (50:50) (% v/v) Strong wash solvent Name Acetonitrile: water(90:10) (% v/v) Injection Volume 5 μl Column oven temperature 40° C.Sample cooler 10° C. Elution Gradient Run time 15 minutes

Mass Parameters:

Start time and end time 0 to 15 minutes Ionization Mode API+ Data TypeSIR data Function Type SIR of one channel Scan time (Sec) 1.00 Dataformat Continuum Span (Da) 0.20

SIR

Channel Mass (Da) Dwell(s) Cone (v) Compound 1 179.04 0.150 12 Tartaricacid Dimethyl ester

Tune Method

Polarity API Positive Corona(kV) 3.5 Kilo volt Cone(V) 12 volt Sourcetemperature (° C.) 150° C. Probe temperature (° C.) 550° C. DesolvationGas Flow 1000 (L/Hr) Cone Gas Flow 50 (L/Hr)

Mass divert Program:

Event Retention time (RT) mins Flow state 1 0.00 Waste 2 (RT_(s) − 1)Waste 3 (RT_(s) − 1) + 0.01 LC 4 (RT_(s) + 1.5) LC 5 (RT_(s) + 1.51)Waste

Gradient Program:

Time (mins) Mobile Phase-A (%) Mobile Phase-B (%) Initial 95 5 5.00 95 56.00 5 95 9.00 5 95 10.00 95 5 15.00 95 5

Mobile Phase A: 0.1% Formic acid in water. (1 ml in 1000 ml water)

Mobile Phase B: Acetonitrile

Diluent: 0.1% Formic acid in water: Acetonitrile (90:10) % v/v

Standard solution: 0.002% concentration in diluent

Sample Preparation: 15mg/ml in diluent

Concentration (% w/w) LOD LOQ Tartaric acid Dimethyl ester 0.0015 0.0046

Calculation:

$\frac{A_{2}}{A_{1}} \times \frac{W_{1}}{W\; 2} \times \frac{100}{Y} \times 106$

Where:

-   A₂=Peak area of Tartaric acid Dimethyl ester impurity in sample-   A₁=Average Peak area of Tartaric acid Dimethyl ester impurity in    standard-   W₁=standard concentration-   W₂=sample concentration-   Y=9.09 (i.e. Theoretical Label claim of Varenicline tartrate in    Varenicline-   Tartrate Maltodextrin Premix (1:10) in %)

G. Nitrosamine Content By Lcms Method-I:

Instrumentation: UPLC equipped with Mass detector(Waters—UPLC equippedwith XEVO-TQ MS Detector with Mass lynx software or Equivalent)

Chromatographic Conditions:

Column Zorbax Eclipse Plus C18 (length: 50 mm, Diameter4.6 mm, Particlesize: 1.8μ) Flow rate 1.0 mL/min Week wash solvent Methanol:water(50:50) Name(% v/v) Strong wash solvent Methanol:water (90:10) Name(%v/v) Injection Volume 6 μl Column oven temperature 30° C. Sample cooler10° C. Elution Gradient Run time 15 minutes

Mass Parameters:

Start time and end time 0 to 15 minutes Ionization Mode ESI+ Data TypeMRM data Function Type MRM of 7 Daughters Scan time (Sec) 1.00 Dataformat Continuum Span (Da) 0.20

MRM for Parent Mass 240.97

Daughter Mass Cone Channel (Da) Dwell(s) Collision energy (v) VoltCompound 1 169.01 0.025 22 20 Nitroso Varenicline impurity 2 181.100.025 32 20 Nitroso Varenicline impurity 3 194.05 0.025 20 20 NitrosoVarenicline impurity

MRM for Parent Mass 278.99

Daughter Collision Cone Channel Mass (Da) Dwell(s) energy (v) VoltCompound 1 127.16 0.025 38 34 Dinitro Nitrosamine impurity 2 156.050.025 30 34 Dinitro Nitrosamine impurity 3 202.11 0.025 24 34 DinitroNitrosamine impurity 4 232.03 0.025 20 34 Dinitro Nitrosamine impurity

Tune Method

Polarity ESI Positive Capillary Volt (KV) 3.5 Cone (V) 32 Dissolvationtemperature (° C.) 600° C. Source Temperature (° C.) 150° C.Dissolvation Gas flow (L/Hr) 1200 Cone Gas Flow (L/Hr) 120 Collision Gasflow (L/Hr) 0.15 Extractor (V) 3.0

Mass divert Program:

Event Retention time (RT) mins Flow state 1 0.00 Waste 2 (RT of NitrosoVarenicline impurity − 0.5) Waste 3 (RT of Nitroso Varenicline impurity− 0.5) + 0.01 LC 4 (RT of Dinitro Nitrosamine impurity + 0.5) LC 5 (RTof Dinitro Nitrosamine impurity + 0.5) + 0.01 Waste

Gradient Program:

Time (mins) Mobile Phase-A (%) Mobile Phase-B (%) 0.01 90 10 0.50 90 107.00 10 90 10.00 10 90 11.00 90 10 15.00 90 10

Mobile Phase A: 0.2% Formic acid in water. (2 ml in 1000 ml water)

Mobile Phase B: Methanol

Diluent: Methanol

Standard solution: 0.000163% conc in diluent

Sample Preparation: 200mg/ml in diluent and sonicate for 3 minute andfilter

Nitroso Varenicline impurity: Parent mass 240.97 three fragments are169.01, 181.0 and 194.05.

Dinitro Nitrosamine impurity: Parent mass 278.99 Four Fragments are127.16, 156.05, 202.11 and 232.03.

S. Retention time LOQ LOD No. Name of impurity (mins) (ppm) (ppm) 1Nitroso Varenicline impurity 3.60 0.032 0.009 2 Dinitro Nitrosamineimpurity 4.21 0.031 0.009

Calculation:

i) Nitroso impurity content in ppm (used for both VareniclineNitrosamine impurity and Dinitro nitrosamine impurity)

$\frac{A_{2}}{A_{1}} \times \frac{W_{1}}{W\; 2} \times \frac{100}{Y} \times 106$

Where:

-   A₂=Sum of peak area of Nitroso Varenicline impurity/Dinitro    Nitrosamine impurity in sample-   A₁=Sum of Average Peak area Nitroso Varenicline impurity/Dinitro    Nitrosamine impurity in standard-   W₁=standard conc of Nitroso Varenicline impurity/Dinitro Nitrosamine    impurity standard-   W₂=Sample concentration-   P=Purity of Nitroso Varenicline impurity/Dinitro Nitrosamine    impurity standard-   Y=9.09 (i.e. Theoretical Label claim of Varenicline tartrate in    Varenicline Tartrate Maltodextrin Premix (1:10) in %)

Nitroso Varenicline impurity: Parent mass 240.97 three fragments are169.01, 181.0 and 194.05.

Dinitro Nitrosamine impurity: Parent mass 278.99 Four Fragments are127.16, 156.05, 202.11 and 232.03.

H. Nitrosamine Content by Lcms Method-II

Instrumentation: UPLC equipped with Mass detector (Waters—UPLC equippedwith XEVO-TQ MS Detector with Mass lynx software or Equivalent)

Chromatographic Conditions:

Column AQUASIL C18 (length: 100 mm, Diameter 4.6 mm, Particle size:3.0μ) Part No: 77503-104630 Flow rate 0.8 mL/min Week wash solvent 0.1%Formic acid in Acetonitrile:water (50:50) Name (% v/v) Strong washsolvent 0.1% Formic acid in Acetonitrile:water (90:10) Name (% v/v)Injection Volume 7 μl Column oven 30° C. temperature Sample cooler 10°C. Elution Gradient Run time 20 minutes

Gradient Program:

Time (mins) Mobile Phase-A (%) Mobile Phase-B (%) 0.01 80 20 5.00 80 207.00 5 95 14.00 5 95 15.00 80 20 20.00 80 20

Mass Parameters:

Start time and end time 0 to 20 minutes Ionization Mode ESI+ Data TypeMRM data Function Type MRM of 2 Daughters Scan time (Sec) 1.00 Dataformat Continuum Span (Da) 0.20

MRM for Parent Mass 218.97

Daughter Collision Cone Channel mass (Da) Dwell(s) energy volt Compound1 145.86 0.025 16.00 30.00 Diamino Nitrosamine 2 188.98 0.025 10.0030.00 Diamino Nitrosamine

Tune Method

Polarity ESI Positive Capillary Volt (KV) 0.35 Cone (V) 30 Desolvationtemperature (° C.) 550° C. Source Temperature (° C.) 150° C. DesolvationGas flow (L/Hr) 1200 Cone Gas Flow (L/Hr) 120 Collision Gas flow (L/Hr)0.15 Extractor (V) 5.0

Mass divert Program:

Event Retention time (RT) mins Flow state 1 0.00 Waste 2 (RT of DiaminoNitrosamine impurity − 1.4) Waste 3 (RT of Diamino Nitrosamine impurity− 1.4) + 0.01 LC 4 (RT of Diamino Nitrosamine impurity + 1.4) LC 5 (RTof Diamino Nitrosamine impurity + 1.4) + 0.01 Waste

Mobile Phase A: 0.01 M Ammonium formate in water. (0.63 gm in 1000 mLwater)

Mobile Phase B: 0.1% Formic acid in methanol (1.0 mL of formic acid in1000 mL methanol)

Diluent: Acetonitrile 100%

Standard solution: 0.000069% concentration in diluent

Sample Preparation: 150mg/ml in diluent and sonicate for 3minute andfilter

Diamino Nitrosamine: Parent mass 218.97 two fragments are 145.86 and188.98.

Injection sequence: (for RT identification)

S. No. Name of solution No. of injections 1 Blank 1 2 StandardPreparation 1

Injection sequence:

S. No. Name of solution No. of injections 1 Blank 2 2 Standard Solution6 3 Blank 1 4 Sample Preparation 2 6 Blank 1 7 Standard Solution (forbracketing) 1

The retention time of Diamino Nitrosamine impurity is as below.

About LOD LOQ Name of Compound RT(min) in ppm in ppm Diamino Nitrosamine6.09 0.009 0.03 impurity

Calculation: For Diamino Nitrosamine impurity content in ppm

$\frac{A_{2}}{A_{1}} \times \frac{W_{1}}{W\; 2} \times \frac{100}{Y} \times 106$

Where:

-   -   A₂=Peak area of Diamino Nitrosamine impurity in sample    -   A₁=Average Peak area Diamino Nitrosamine impurity in standard    -   W₁=standard conc of Nitroso Varenicline impurity/Dinitro        Nitrosamine impurity standard    -   W₂=Sample concentration    -   P=Purity of Diamino Nitrosamine impurity standard    -   Y=9.09 (i.e. Theoretical Label claim of Varenicline tartrate in        Varenicline Tartrate Maltodextrin Premix (1:10) in %)

Discussion:

Two Related Substance methods by HPLC were developed for analyzingVarenicline base (Stage 3) for quantifying all impurities of having asimilar chromophore of Varenicline. The same two HPLC methods wereadopted for analyzing the Varenicline Tartrate Maltodextrin Premix APIfor quantifying the respected impurities. A third additional RS methodby HPLC was developed for analyzing two additional impurities viz.N-methyl Varenicline and Varenicline-N-Gluoside which could form due toreaction of degradation products of Maltodextrin with Varenicline.

Two LCMS methods were developed for analyzing monomethyl and dimethylesters of tartaric acid as impurities in Varenicline TartrateMaltodextrin premix API.

Two LCMS methods were developed for quantifying the nitrosamineimpurities in Varenicline Tartrate Maltodextrin Premix API.

All the impurities were prepared and qualified by applicant. Also allthe above analytical methods were developed and validated by applicant.

Three possible nitrosamine impurities should be controlled in theVarenicline Tartrate Maltodextrin Premix API. However, FDA's publishedmethod controls only varenicline nitrosamine impurity.

FDA's method is used for analyzing plain API of Varenicline Tartrate. Incontrast, the API analyzed in Example 8 is Varenicline TartrateMaltodextrin Premix API (1:10). The Premix API contains only about 10%w/w Varenicline Tartrate drug substance. This is a major challenge thatwas faced for developing method in analyzing nitrosamine impurities inthe instant Premix API.

A comparison and advantages of applicant's method (disclosed in Example8 above) over FDA's method for analyzing nitrosamines is provided inTable 22.

TABLE 22 Comparison and Advantages of in-house versus FDA Method forNitrosamines S.No Parameter In-house FDA Method 1 Instrument LCMS/MSLC-HRMS 2 Nitrosamine Two methods were developed for Method is suitablefor Method analyzing three nitrosamines viz. only Varenicline dinitronitrosamine, diamino Nitrosamine. nitrosamine and VareniclineNitrosamine. 3 Detector Mode Extracted daughter ions from parentExtracted parent ion m/z ESI ion Mass 240.97 (MRM mode). 241.1084 (SIMmode) for Daughter Mass Varenicline Nitrosamine.(Da).169.01,181.10,194.05. Multiple Selected ion monitoring reactionmonitoring (MRM) offers (SIM) is suitable for the significantimprovements for the screening and screening and confirmation ofconfirmation of molecules molecules, especially in more complex inrelatively simple matrices. matrices. 4 Analytical Both methods werevalidated as per Partially validated like method ICH Q2 R1 anddemonstrated that it Is LOD & LOQ. Linearity Validation suitable for itsintended purpose. range LOQ of 1.0 to Linearity range was achieved from200 ppm. LOQ to 7.5 ppm. 5 LOD/LOQ value Achieved LOD/LOQ of 0.01 ppm &reported LOD is 0.2 ppm 0.03 ppm respectively for all & LOQ value is 1.0ppm nitrosamine. The guideline for Varenicline recommended to achieveLOQ of 0.03 nitrosamine. ppm for nitrosamines 6 Spec Limit Suitable forthe limit NMT 5.26 ppm Limit was not provided. for each nitrosamine andtotal nitrosamine limit NMT 7.74 ppm.

Example 9 Preparation of1-(4,5-Diamino-10-Aza-Tricyclo[6.3.1.0^(2,7)]Dodeca-2(7),3,5-Trien-10-YL)-2,2,2-Trifluoro-Ethanone

1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoroethanone(100.0 g, 0.2896 mole) was hydrogenated in methanol (1000 mL) underhydrogen (0.5-1. 0 kg/cm²) atmosphere in the presence of 10% Palladiumon carbon (10.0 g, 50% wet). After 3 hours, the reaction mass wasanalyzed by qualitative HPLC to confirm the completion of the reaction.Thereafter, the reaction mass was filtered through celite pad and rinsedwith methanol (100 ml). The filtrate was concentrated completely at30-35° C. under reduced pressure. Hexanes was added to the concentratedmass and distilled completely 30-35° C. under reduced pressure to removetraces of methanol. The mass was stirred with hexanes, the precipitatedsolid was filtered and washed with hexanes. The wet material was driedat 40-45° C. under reduced pressure for 8 hours. Yield: 82.0 g (100%).

Example 10 Preparation Of 1-(5,8,14-Triazatetracyclo[10.3.1.02,11.0.4,9]Hexadeca-2(11),3,5,7,9-Pentaene)-2,2,2-Trifluoro-Ethanone

The mixture of1-(4,5-Diamino-10-aza-tricyclo[6.3.1.02,7]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone(73.0 g, 0.256 mole), methanol (146 mL) and water (146 mL) were treatedwith 40% aqueous glyoxal (40.88 g, 0.2816 mole) and aqueous solution ofsodium bisulfate (58.58 g, 0.563 mole in 117.5 mL of water) at 55-60° C.for 3 hours. Thereafter, cooled the mass to 20-30° C., water (730 mL,10.0 volume) was added and stirred at 20-30° C. for 2 hours. Theobtained solid was filtered and slurry washed with water. The semi-driedcrude product was crystallized from methanol. Yield: 58.0 g.

Example 11 Preparation of7,8,9,10-Tetrahydro-6,10-Methano-6H-Pyrazino[2, 3-H][3]Benzazepine:(Varenicline Free Base)

1-(5,8,14-triazatetracyclo[10.3.1.0 2,11.0.4,9] hexadeca-2(11),3,5,7,9-p entaene)-2,2,2-trifluoroethanone is deprotected using sodium carbonatein 50% aqueous methanol to give7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino [2, 3-h][3] benzazepine(Varenicline free base).

Thus, 1-(5,8,14-triazatetracyclo[10.3.1.0 2,11.0.4,9]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoroethanone (48.0 g, 0.1562mole) in methanol (290 mL) was stirred with aqueous Sodium carbonatesolution (33.12 g in 300 mL of water) at 65-70° C. for 3 hours. Thereaction mass was filtered and the residue was washed with methanol(48.0 mL).

The combined filtrate was concentrated at 30-35° C. under reducedpressure. The concentrated reaction mass was saturated with sodiumchloride and extracted with methylene dichloride. The organic layer waswashed with 25% brine solution and treated with activated carbon (5.0g). The organic layer was concentrated at 30-35° C. to oily mass andco-distilled at 30-35° C. with methyl tert-butyl ether (96 mL) to removetraces of Methylene dichloride. Methyl tert-butyl ether (192 mL) wasadded to the concentrated mass and stirred at 5-10° C. for 3 hours. Theproduct was isolated by filtration and washed with chilled methyltert-butyl ether twice. The wet material is dried at 35-40° C. undervacuum. Yield: 27.5 g.

A. General procedure for the purification Varenicline free base usingorganic or inorganic acid:

A solution of Varenicline free base (100.0 g, 0.4733 mol) in methylenedichloride (500 mL, 5.0 vol) was stirred with the aqueous solution oforganic or Inorganic acid (1.2 eq, 500 mL of water, 5.0 vol) for 30 minat 25-30° C. The aqueous layer containing corresponding Varenicline saltsolution was separated and stirred with methylene dichloride (2×250mL)to remove nitrosamine impurity by solvent extraction. Thereafter, theaqueous layer was basified (pH 8.5 to 9.5) with aqueous Sodium carbonatesolution (2.2 eq in 8.0 volume of water) and extracted the freevarenicline base three times with methylene dichloride (3×10.0 volume).The combined organic layer was washed with brine solution and treatedwith activated carbon (2.0 g). The organic layer was concentrated tooily mass and co-distilled with methyl tert-butyl ether to remove tracesof methylene dichloride. methyl tert-butyl ether (80 mL, 4.0 volume) wasadded to the concentrated mass and stirred at 5-10° C. for 3 hours. Theproduct was isolated by filtration and washed with chilled methyltert-butyl ether by twice. The wet material was dried at 40° C. undervacuum. Yield: 62.0 g

Example 12 Purification of Varenicline Free Base using L-(+)-TartaricAcid

A solution of Varenicline free base (50.0 g) in methylene dichloride(250 mL) was stirred with the aqueous solution of L-(+)-Tartaric acid(1.2 eq, 39.08 g in 250 mL of water). The aqueous layer containingVarenicline tartrate salt was stirred with methylene dichloride (3×150ml) to remove the nitrosamine impurity by solvent extraction.Thereafter, follow the general procedure for the isolation ofVarenicline base from the aqueous layer. Yield: 31.00 g.

Example 13 Purification of Varenicline Free Base using Fumeric Acid

A solution of Varenicline free base (20.0 g) in methylene dichloride(100 mL) was stirred with the aqueous solution of Fumaric acid (13.18 g,1.2 eq in 100 mL of water). The aqueous layer containing Vareniclinefumarate salt was stirred with methylene dichloride to remove thenitrosamine impurity by solvent extraction. Thereafter, follow thegeneral procedure for the isolation of Varenicline base from the aqueouslayer. Yield: 14.0 g

Example 14 Purification of Varenicline Free Base using Lactic Acid

A solution of Varenicline free base (20.0 g) in methylene dichloride(100 mL) was stirred with the aqueous solution of Lactic acid (10.23 g,1.2 eq in 100 mL of water). The aqueous layer containing Vareniclinelactate salt was stirred with methylene dichloride to remove thenitrosamine impurity by solvent extraction. Thereafter, follow thegeneral procedure for the isolation of Varenicline base from the aqueouslayer Yield: 12.4 g

Example 15 Purification of Varenicline Free Base using Malic Acid

A solution of Varenicline free base (20.0 g) in methylene dichloride(100 mL) was stirred with the aqueous solution of Malic acid (15.23 g,1.0 eq in 100 mL of water). The aqueous layer containing Vareniclinemalate salt was stirred with methylene dichloride to remove thenitrosamine impurity by solvent extraction. Thereafter, follow thegeneral procedure for the isolation of Varenicline base from the aqueouslayer. Yield: 13.0 g.

Example 16 Purification of Varenicline Free Base using Malonic Acid

A solution of Varenicline free base (20.0 g) in methylene dichloride(100 ml) was stirred with the aqueous solution of Malonic acid (11.82 g,1.2 eq in 100 ml of water). The aqueous layer containing Vareniclinemalonate was stirred with methylene dichloride to remove the nitrosamineimpurity by solvent extraction. Thereafter, follow the general procedurefor the isolation of Varenicline base from the aqueous layer. Yield:13.6 g

Example 17 Purification of Varenicline Free Base using Hydrochloric Acid

A solution of Varenicline free base (10.0 g) in methylene dichloride(50.0 ml) was stirred with the aqueous solution of hydrochloric acid(6.9 g of 30% aqueous HC1, in 50 ml of water). The aqueous layercontaining Varenicline hydrochloride was stirred with methylenedichloride to remove the nitrosamine impurity by solvent extraction.Thereafter, follow the general procedure for the isolation ofVarenicline base from the aqueous layer. Yield 8.0 g

Example 18 Purification of Varenicline Free Base using Succinic Acid

A solution of Varenicline free base (25.0 g) in methylene dichloride(125 mL) was stirred with the aqueous solution of succinic acid (16.77g, 1.2 eq in 125 mL of water). The aqueous layer containing Vareniclinesuccinate was stirred with methylene dichloride to remove thenitrosamine impurity by solvent extraction. Thereafter, follow thegeneral procedure for the isolation of Varenicline base from the aqueouslayer. Yield 15.6 g

Example 19 Purification of Varenicline Free Base using Oxalic Acid

A solution of Varenicline free base (20.0 g) in methylene dichloride(100 ml) was stirred with the aqueous solution of Oxalic acid (14.35 g,1.2 eq in 100 ml of water). The aqueous layer containing Vareniclineoxalate was stirred with methylene dichloride to remove the nitrosamineimpurity by solvent extraction. Thereafter, follow the general procedurefor the isolation of Varenicline base from the aqueous layer. Yield:14.6 g.

Example 20 Purification of Varenicline Free Base using Citric Acid

A solution of Varenicline free base (25.0 g) in methylene dichloride(125 mL) was stirred with the aqueous solution of citric acid (27.28 g,1.2 eq in 125 mL of water). The aqueous layer containing Vareniclinecitrate was stirred with methylene dichloride to remove the nitrosamineimpurity by solvent extraction. Thereafter, follow the general procedurefor the isolation of Varenicline base from the aqueous layer. Yield 16.2g.

Example 21 Purification of Varenicline Free Base using Reduction Process

A solution of Varenicline free base (5.0 g) in methanol (50 mL) wasstirred under hydrogen (6.0 kg/cm²) pressure in the presence of 10%Palladium on carbon (0.5 g, 50% wet) at 25-35° C. After 6 hours and thereaction mass was filtered through celite pad and rinsed with methanol(50 ml). The filtrate was distilled completely under reduced pressureand co-distilled with methyl tert-butyl ether to remove traces ofmethanol & water. methyl tert-butyl ether (50.0 mL, 10.0 volume) wasadded to the concentrated mass and stirred at 5-10° C. for 3 hours. Theproduct was isolated by filtration and washed with chilled methyltert-butyl ether by twice. The wet material was dried at 40° C. undervacuum. Yield:4.2 g

Example 22 Varenicline Tartrate Maltodextrin Premix

Varenicline free base (7 g) was dissolved in methanol (140 ml) at 25-30°C. In a separate flask, tartaric acid (4.92g) was dissolved in 70 mlwater at 25-30° C. Varenicline solution was mixed with tartaric acidsolution at 25-35° C. The resulting clear solution was stirred for 30min at 25-35° C. to form the Varenicline tartrate salt solution.Maltodextrin (119.84 g) was dissolved in water (420.53 ml) at 25-35° C.separately and added this Maltodextrin solution into Vareniclinetartrate solution prepared earlier. The resulting clear solution wasstirred for 30 minutes, filtered through a micron filter and washed withwater (2×70 ml). The clear filtrate was subjected to spray drying usinga spray dryer to obtain the amorphous Varenicline Tartrate MaltodextrinPremix (1:10) API. Yield: 130.0 g. Purity by HPLC: 99.99%.

Example 23 Nitrosamine Impurities Content in Varenicline Base Before andAfter Purification using Organic and Inorganic Acid

Preparation of Varenicline Tartrate Maltodextrin Premix (1:10) API Fromthe key starting material,1-(4,5-Dinitro-10-aza-tricyclo[6.310^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoroethanoneand purification of varenicline base to eliminate nitrosamine impuritiesby using organic acids having the pKa preferably between 2 and 6, orinorganic acid are demonstrated in Examples 9-22.

The graphical presentation of purification of varenicline free base toeliminate nitrosamine impurities using organic or inorganic acids andalso by catalytic hydrogenation in the presence of palladium on charcoalis provided in FIG. 11.

Table 23 provides nitrosamine contents in varenicline base before andafter purification using organic or inorganic acids (based on Examples12-21). Organic acids are selected preferably having the pKa between 2and 6. Also, it was observed that varenicline base contaminated withvarenicline nitrosamine is subjected to reduction under hydrogenpressure in the presence of palladium on carbon eliminates thevarenicline nitrosamine impurity (Refer Example—21 and S. No. 10 ofTable 23) to the desired limit.

TABLE 23 Nitrosamine Contents in Varenicline Base Before and AfterPurification Using Organic or Inorganic Acids Dinitro Diamino Inorganicand Varenicline Nitrosamine nitrosamine nitrosamine Organic acidimpurity in ppm Impurity in ppm Impurity in ppm used for Before AfterBefore After Before After S. No purification Purification PurificationPurif. Purifi. Purifi. Purifi.  1 L-(+)-Tartaric acid 16.57 1.76 ND NDND ND  2 Fumeric acid 16.57 2.93 ND ND ND ND  3 Lactic acid 19.22 3.08ND ND ND ND  4 Malic acid 19.22 4.48 ND ND ND ND  5 MaIonic acid 19.223.87 ND ND ND ND  6 Hydrochloric acid 16.57 2.26 ND ND ND ND  7 Succinicacid 16.57 1.85 ND ND ND ND  8 Oxalic acid 16.57 2.77 ND ND ND ND  9Citric acid 16.57 1.42 ND ND ND ND 10 Reduction by Pd/C 19.22 0.75 ND NDND ND ND: Not Detected Note: Dinitro nitrosamine Impurity and Diaminonitrosamine Impurity both are controlled in Stage-3 crude itself.

Conclusion: This result demonstrates that nitrosamine can be eliminatedfrom the varenicline free base (crude) by forming salts with variousorganic or inorganic salts in aqueous solution and unprotanatednitrosamines are removed by solvent extraction. Thereafter, pure freevarenicline base can be isolated from the aqueous varenicline saltsolution by basification (purification of varenicline by acid-basetreatment). Varenicline base was analyzed by LCMS for determiningnitrosamine contents before and after purification of varenicline base.

Those of ordinary skill in the art will recognize, or be able toascertain using no more than routine experimentation, equivalents to thespecific embodiments of the invention described herein. Such equivalentsare intended to be encompassed by the following claims.

What is claimed is:
 1. A compound suitable for use as an activepharmaceutical ingredient, comprising substantially pure vareniclinetartrate.
 2. The compound of claim 1, wherein about 1.7 mg of thevarenicline tartrate, or about 0.85 mg of the varenicline tartrate, hasless than 100 ppm of N-nitroso-varenicline impurity.
 3. The compound ofclaim 1, wherein about 1.7 mg of the varenicline tartrate, or about 0.85mg of the varenicline tartrate, has less than 50 ppm ofN-nitroso-varenicline impurity.
 4. The compound of claim 1, whereinabout 1.7 mg of the varenicline tartrate, or about 0.85 mg of thevarenicline tartrate, has less than 25 ppm of N-nitroso-vareniclineimpurity.
 5. The compound of claim 1, wherein about 1.7 mg of thevarenicline tartrate, or about 0.85 mg of the varenicline tartrate, hasless than 19 ppm of N-nitroso-varenicline impurity.
 6. The compound ofclaim 1, wherein about 1.7 mg of the varenicline tartrate, or about 0.85mg of the varenicline tartrate, has about 5 ppm or less ofN-nitroso-varenicline impurity.
 7. A process for preparation of7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine,(2R,3R)-2,3-dihydroxy butanedioate.maltodextrin, comprisingthe steps of: (a) contacting a reducing agent with1-(4,5-Dinitro-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanoneto form1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone;(b) contacting Glyoxal solution in water, a catalyst and a solvent with1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanoneto form1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanone;(c) contacting sodium carbonate solution and methanol with1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanoneto form crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine; (d)purifying crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine byacid-base treatment substantially eliminate impurities and to formpurified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine; and(e) contacting purified7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine withL-(+) tartaric acid, maltodextrin, methanol and water to form7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate. maltodextrin premix(1:10).
 8. The process of claim 7, wherein the7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedio ate.malto dextrin premix(1:10) is substantially free from nitrosamine impurities.
 9. The processof claim 7, wherein 1-(4,5-diamino-10-aza-tricyclo[6.3.1.0^(2,7)]dodeca-2(7),3,5-trien-10-yl)-2,2,2-trifluoro-ethanone is precipitatedusing hexane.
 10. The process of claim 7, wherein1-(5,8,14-triazatetracyclo[10.3.1.0^(2,11)0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanoneis precipitated using water.
 11. The process of claim 10, wherein theprecipitated 1-(5,8,14-triazatetracyclo[10.3.1.0²′¹¹0.0.^(4,9)]hexadeca-2(11),3,5,7,9-pentaene)-2,2,2-trifluoro-ethanoneis recrystallized using methanol.
 12. The process of claim 7, whereincrude 7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepineis isolated from a reaction mass by a process, comprising the steps of:(a) cooling and filtering the reaction mass to form a filtrate and a wetcake; (b) distilling the filtrate to remove methanol; (c) adding sodiumchloride solution to the distilled filtrate; (d) extracting raw7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine usingmethylene chloride and washing with sodium chloride solution; (e)treating raw7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine withactivated carbon, washing with methylene dichloride and filtering themethylene dichloride through a hyflo bed; (f) distilling out methylenedichloride followed by co-distilling with tertiary butyl methyl ether toform a semi dried product; (g) adding tertiary butyl methyl ether to thesemi dried product; and (i) isolating crude7,8,9,10-Tetrahydro-6,10-methano-6H-pyrazino[2,3-h][3]benzazepine. 13.The process of claim 7, wherein about 1.7 mg, or about 0.85 mg, of thepurified 7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate. maltodextrin premix(1:10) has less than 25 ppm N-nitroso-varenicline impurity.
 14. Theprocess of claim 7, wherein step (e) is conducted at a temperature fromabout 27° C. to about 33° C. and the7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino [2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate.maltodextrin premix(1:10) is isolated by a spray drying process.
 15. The process of claim14, wherein the spray drying process produces nearly spherical shapedparticles.
 16. The process of claim 15, wherein the7,8,9,10-tetrahydro-6,10-methano-6h-pyrazino[2,3-h][3]benzazepine,(2r,3r)-2,3-dihydroxy butanedioate is essentially uniformlydispersed in maltodextrin matrix in the particles.
 17. A method oftreating nicotine dependency, addiction and withdrawal in a subject inneed thereof, comprising providing a pharmaceutical compositioncomprising about 0.5 mg to about 1 mg substantially pure vareniclinefree base; and orally administering the composition in one or more dailydoses, wherein the subject receives a total of no more than about 37 ngof N-nitroso-varenicline impurity per day as measured by LC-ESI-HRMS,HPLC or LCMS.
 18. The method of claim 17, wherein the compositioncomprises about 1 mg of varenicline free base that has less than 25 ppmof N-nitroso-varenicline impurity.
 19. The method of claim 17, whereinthe composition is orally administered one week before a date set by thesubject to attempt to stop smoking.
 20. The method of claim 17, whereinthe treatment is effective in the subject to quit smoking between days 8and 35 of treatment.
 21. The method of claim 17, wherein the compositionis administered at a dose of about 1 mg varenicline free base.
 22. Themethod of claim 17, wherein the composition is administered in a regimencomprising: (a) 0.5 mg varenicline free base once daily for days 1-3 ofthe treatment; (b) 0.5 mg varenicline free base twice daily for days 4-7of the treatment; and (c) 1 mg varenicline free base twice daily afterday 7 of the treatment.
 23. The method of claim 22, wherein the patientis treated for 12 weeks.
 24. A pharmaceutical composition, comprisingsubstantially pure varenicline tartrate and at least one excipient. 25.The pharmaceutical composition of claim 24, wherein the compositioncomprises about 0.5 mg to about 1 mg varenicline free base and is in theform of a tablet or capsule.
 26. The pharmaceutical composition of claim25, wherein N-nitroso-varenicline impurity is present in an amount ofless than 50 ppm per tablet or capsule as measured by LC-ESI-HRMS. 27.The pharmaceutical composition of claim 26, wherein the compositionfurther comprises croscarmellose sodium, microcrystalline cellulose, andstearic acid.
 28. The pharmaceutical composition of claim 26, whereinthe composition further comprises hydroxypropyl cellulose, hypromellose,talc, and titanium dioxide.
 29. The pharmaceutical composition of claim25, wherein the tablet or capsule comprises 0.5 mg varenicline free baseand about 5 ppm or less of N-nitroso-varenicline impurity.
 30. Thepharmaceutical composition of claim 25, wherein the tablet or capsulecomprises 1 mg varenicline free base and about 5 ppm or less ofN-nitroso-varenicline impurity.